Surveying 'with' Raptors

Surveying ‘for’ raptors is a well established discipline in ecology, however, the latest scientific research is now surveying ‘with’ raptors.

Golden Eagle (by John Carey)

The problem of climate change is increasingly being recognised politically and by the general public. The social, environmental and economic impacts of its actions are being felt worldwide. The equally important mechanism of environmental degradation; human-induced biodiversity loss, is threatening essential ‘ecosystem service’. Ecosystem services include clean water, air and soil, resources upon which our societies and economies depend. In order to overcome or prevent in the future, further, ecosystem service collapse, we must first identify, monitor and recognize the mechanisms involved. Therefore environmental monitoring is of paramount importance. All elements of the environment cannot be monitored given the complexity of the system. Therefore, the most informative and cost effective method must be sought. As a group raptors show considerable latent, potential as monitoring tools. They are often easily detected and monitored. Their presence or absence can be easily noted. As top predators, environmental effects are amplified within their communities. Raptors are typically highly sensitive to a range of environmental pressures, such as prey fluctuations, habitat change, human disturbance and contaminants.  

Marsh Harrier (by Killian Mullarney)

The role of raptor populations as valuable sentinels of environmental health is being increasingly recognised throughout numerous disciplines. As apex predators previous studies have found them invaluable indicators of the presence of pollutants, toxins and introduced species in the environment. The most well documented example, of proven, effective monitoring ‘with’ raptors, revealed changes in organochlorines in the environment. In Ireland, ecosystems are currently under the damaging effect of two introduced small mammal species and toxins. The introduction and expansion of two non-native small mammal species in Ireland, the Bank Vole and the Greater White-toothed Shrew could have wide ranging impacts within ecosystems throughout the country. Three distinct geographical areas have been defined in relation to small mammals, one with indigenous species only, another with indigenous plus the Bank Vole and a final type with indigenous plus both introduced species. The Bank Vole currently occupy a third of the land mass of Ireland. Genetic studies have established that the Irish population was founded from a small number of individual introduced from Germany in the 1920’s. The populations estimated rate of spread is 3 km per year. The Greater White-toothed Shrew occurs in a limited area within the range of the Bank Vole, it can occur at high densities and both species are now common within the regurgitated pellets of local raptors. This indicates a major shift in small mammal communities recently.

Studies have indicated that where the range of the Bank Vole and Greater White-toothed Shrew overlap they have a synergistic relationship which negatively effects the abundance of the Wood Mouse populations and can cause local extinction in the Pygmy Shrews. Interspecific competition and disease have both been implicated as causing factors. As the range of the two introduced small mammals expands so this negative effect for the Wood Mouse and Pygmy Shrew will be replicated into the new areas.

The effects of the Bank Vole and the Greater White-toothed Shrew are being felt by avian predators of small mammals. The Barn Owl, Long-eared Owl and Kestrel are in particular implicated. Barn Owl research has indicated that the Bank Voles and the Greater White-toothed Shrews presence in the diet can have profound effects on their breeding success. In areas of the south west where Bank Voles occur at high densities the species is seen to constitute 80% of Barn Owls’ diet.  Given the overlap in diet of these three species it can be envisioned that the Bank Voles and Greater White-toothed Shrews are impacting upon the Kestrel and Long-eared Owl also. Pygmy Shrews have been demonstrated to comprise 7%-14% of the mammalian composition of Barn Owl diets in Ireland. The Wood Mouse in Ireland represents 70% of the diet of the Long-eared Owl. Increasingly, the value of using apex predators as indicators of environmental health is being promoted. Are the introduced small mammals impacting the ecology of raptors and what consequences will their spread have for the future outlook of the wider countryside?

Raptors that prey on the Brown Rats or the House Mouse can fall victim to secondary poisoning. Due to the depleted small mammal community in Ireland these small mammals regularly occur in the diets of raptors in Ireland. Barn Owls within the Bank Vole and Greater White-toothed Shrew range may experience lower levels of secondary poisoning, a similar situation may be experienced by Kestrels and Long-eared Owls. 

Kestrel (Clive Timmons)

As small mammal specialists the Barn Owl, the Kestrel and the Long-eared Owl can act as biodeterminators, in establishing the wider significance of a small mammal introduction and secondary poisoning from rodenticides on Ireland’s ecosystems. By studying ecologically damaging agents in the environment 'with' raptors, efforts can be made to prevent, minimize and mitigate their effects in the future.

Raptor Facts and Figures

The breeding season is starting to slow down and show the first signs of it coming to an inevitable close. Kestrel fieldwork has been completed for the year, with close to 35% of monitored nests having failed or experienced predation. This is quite a bad success rate for Kestrels, who normally perform a lot better. No doubt the abysmal weather we have all suffered through will have played a central role in this. Barn Owls are known nationally to be the rarest of our three study species and are Red-listed in Ireland. In West Offaly this scarcity is replicated. There are roughly twice the number of Kestrels as Barn Owls and three times more Long-eared Owls.  

Barn Owl siblings - pictured by Padraig Cregg

The situation with Long-eared Owls in the country is less clear owing to less work carried out on the species nationally. In my home patch, of West Offaly, many of the traditional nest sites haven’t shown signs of breeding, ie calling chicks, however the overall numbers of breeding Long-eared Owl sites which we now know about has increased. This however is probable down to the increased efforts put into their monitoring this season. Mid August will see the completion of my final acoustic survey for calling Long-eared Owl chicks. On this date, a more comprehensive picture will emerge, but even at this point I can say that Long-eared Owls are the most common raptor species within my intensive study area in West Offaly.

Long-eared Owl - pictured by John Lusby

And on a completely unrelated note.....

Rowan trees grow the length of my garden, a linear orchard of seasonal berries for the avian community. But I had a thought, could predators and in this case a Sparrowhawk learn to associate an obvious prey food source like this with prey? Although hawks are numbered among the more intelligent of birds, this is possibly too great a mental leap. What I do know is my local Sparrowhawk is enjoying the frugivore birds in my garden. Bullfinches, Blackbirds and Starlings seem to be the favourites. A new selling point for the humble Rowan tree, ‘buy a Rowan attract a Sparrowhawk’....I’m sold.

Barn Owl Nest Watch 2012

John Lusby, Raptor Conservation Officer with BirdWatch Ireland, has partnered up of late with the Mooney Show on RTE Radio One. A camera has been placed (under license) in a Barn Owl nest box in Kerry. The webcam, which you can view by clicking on the link below, gives an intimate view of the breeding behaviour of Barn Owls.

The nest box was put in place in 2009, after a previous nest site in the roof of the building was destroyed, and the Barn Owls have nested there ever since.

http://www.rte.ie/radio/mooneygoeswild/features/mooneycam/

Eerie Calls in the Night

I have been out on the prowl, over the last few nights trying to track down breeding Barn Owls. With most of the countries breeding population monitored at this point in the season, I am simply seeking some of the remaining outliers, to create a fuller picture of breeding status of this Red-Listed Species. Several of these sites have proven active and even seem to have bred, which is a positive in what has been an all round bad breeding season for many species.

Barn Owl - pictured by Padraig Cregg

Last night I visited a large ruined mansion not far from Banagher. The fact that the building wasn’t far from a road which gets a moderate level of usage allowed me some leeway in terms of my approach. I needn’t have worries though as I could hear calling Barn Owls has soon as the chunky thud of my diesel motor subsided. I could hear four birds in total, but it can be hard to be precise on the number of birds present as they may simply be moving about. I definitely saw three owls. My best guess was that there were two fledgling Barn Owls who were flying about along with their parents. The parents were calling back and forth to one another, a behaviour more typical of earlier in the season. This renewed courtship could result in a second breeding attempt by the parents, but given the bad season it is unlikely that it will amount to much. Barn Owls can have a second brood in a year but this is quite unusual in Ireland. In fact a brood as late as October has been recorded by BirdWatch Ireland staff.

Barn Owl white wash - pictured by Padraig Cregg

Although of course a nocturnal species, day time visits to likely buildings can be very informative also. Should you hear the stereotypical snoring begging call during the day it is most often a sign that the chicks are still quite young. Pellets and white wash, are, though the main daytime signs to watch out for. Above is a picture of Barn Owl white wash, note the thin white line almost like a dribble of white paint, which identifies it as Barn Owl white wash. Once birds are seen to be present, through day or nighttime observations, the building is revisited to ring the occupants, pictured below.  

Barn Owl ringing - pictured by Padraig Cregg

The Peregrine Falcon

The Peregrine Falcon is a beautiful bird, I think few would argue, but man-o-man what an ugly alarm call. I have been diversifying to a degree of late, moving away from my usual fair of Owls and Kestrels to the more regal Peregrine. Sitting atop their food chain has instilled a confidence to the species which other smaller raptors lack. Whenever I approach a nest site, the resident pair circle and berate my intrusion with their alarm calls. As with Barn Owls and Kestrels, ruined builds are an important nesting site for the species. Before entering into this field of work I would never have imagined or probably of have noticed the sheer number of ruined castles, mansions and cottages in the country. This second life of the buildings, makes them of great conservation importance. Fledgling Peregrines below.

The inside of a Peregrine occupied ruined building, is a veritable who’s who of the local avian community. The ground under foot crackles, with the crunch of miscellaneous bones of past meals. Although Peregrines are often implicated as racing pigeon glutens, Jackdaw carcases in my experience make up a large chunk of the diet. This is an unsurprising chose on the part of the Peregrines, due to the fact that Jackdaws are often also in residence in the ruins.

A lot of fiction surrounds Peregrines and the speeds which they can reach during a stoop while hunting. Let me try and clear this up, between 160km and 410km has been suggested by various authors. The truth is that birds have been seen to reach speeds of 200km and that speeds of 240km are theoretically possible for the species! During the stoop, Peregrines drop from a great height, folding their wings back and slightly away from their bodies, creating a tear drop shape. The unsuspecting prey is often killed in the midair collision, with the Peregrine’s talons aiming for the head. If the prey is still alive after collision, it is dispatched on the ground with the beak.     

Peregrines are a real success story; with the changes in the laws controlling the use of pesticides the species is making a comeback. Being both an urban and rural species, a close encounter with a Peregrine could be just around the corner, why not keep an eye out in your local patch for this sleek speedster.

Dusk on the Shannon, and all is well with the world.

The Shannon - by Padraig Cregg

Irish Stoat

I was on the way to work when a flash of brown, sped across the road. It was a stoat, with a rodent in its mouth. In its surprise and haste to avoid my car wheel it dropped its prize. Knowing their cheek, I pulled over, jumped out of my car with my camera in hand just in time to get this shot of the stoat returning to retrieve its meal. The Irish Stoat, which is an unique sub species, can be identified by the ragged edge of white on the chest, as apposed to the smooth edge seen on continental stoats.

Irish Stoat - by Padraig Cregg

Starving

I spoke in my last post of the introduction of two new small mammal species, this week I have seen firsthand the devastating effects on Barn Owls.

I have been ringing Barn Owl chicks at nests in Tipperary and east Limerick in the past few days. The chicks which we have been finding have been in very bad health and perilously under weight. The chicks are lethargic, under sized, their feathers are not as developed as they should be for their age and light. So light in fact that little hope can be held out for the survival of many of the individuals encountered. Some of the chicks we found weighed just over half of the appropriate weight expected for their age. The brood sizes were also depressed. Many of the nests contained the grizzly, mummified remains of nest mates who hadn’t made it. Chicks often seemed to be experiencing some form of intestinal problem; covered in faecal matter, the smell would turn your stomach.

What on earth is going on with these Barn Owls?

Firstly let me lay out a few facts. This area of Tipperary and east Limerick is the strong hold of one of our latest small mammal species arrivals, the Greater White-toothed Shrew. The Greater White-toothed Shrew occurs at very high densities within this region. Where this species occurs in any great numbers it constitutes the majority of the diet of the Barn Owl. Barn Owl chicks in this ‘Shrew Zone’ are being feed predominately on Greater White-toothed Shrews. These facts seem to implicate this Shrew species. Furthermore, the fact that this shrew species occurs at such high densities in the area would suggest that it isn’t quantity of food which is the problem for Barn Owls but quality.

Following this line of inquiry BirdWatch Ireland in collaboration with Queen’s University are examining the nutritional value of the Greater White-toothed Shrew. Well feed chicks that are starving to death seems counter intuitive, although a comparable situation has been well documented among men who found themselves isolated in the Canadian wilderness. Over a hundred years ago when people used to spend the winter trapping for fur in Canada’s vast wilderness they would subsist on a diet of hare meat. These men would then often starve to death, although they were seemingly well feed. The problem resides in the fact that although hare meat is nutritious in many respects, it lacks many essential vitamins and minerals. The men were expending more vitamins and minerals in digesting the hare meat than the meat was providing in return!

Could Barn Owls be experiencing a similar paradox, only time and further research will unlock this riddle.

Invasion Species on the Menu for Ireland's Raptors

Until recently there were five small mammal species on the island of Ireland, that number has now grown by two with the discovery of the Bank Vole and the Greater White-toothed Shrew. The Bank Vole was first discovered in Listowel in County Kerry in 1964, recent DNA evidence has point to the species having been accidentally introduced from Germany in the 1920’s to West Limerick. The Bank Vole has thrived in the Ireland since its introduction and currently occupies a third of the country, while continuing to expand its range. The Greater White-toothed Shrew was discovered more recently, in 2008 while research was being carried out which involved raptor diet analysis, by BirdWatch Ireland, University College Cork and Queen’s University. The species is also expanding its current range out from an area of West Limerick and South Tipperary. Where these two invasive small mammal species occur they can represent a significant proportion of the diet of birds of prey. In some areas of South Tipperary Barn Owls (pictured below my Mick Boldger) have been seen to be feeding almost exclusively on the Greater White-toothed Shrew.

The introduction of these two invasive small mammal species has created distinct small mammal communities across the island. This novel layering up and down of the country, sees three unique regions, one with only native small mammals, another with the native species plus the Bank Vole and the final one which has both invasive species plus our natives. This geographically diversity of assemblages has generated unique ecological effects on both avian predator and on our native Wood Mouse and Pygmy Shrew. The extent of the influence which the Bank Vole and Greater White-toothed Shrew (pictured below by John Murphy) have on raptors seems to be wide-ranging. As of yet little research has been carried out on the Kestrel or the Long-eared Owl. In Barn Owls the Bank Vole can make up to 80% of the diet where they occur in high densities and seem to be having a positive effect on breeding success of the species. The species is also found at higher densities where the Bank Vole is abundant. The situation is more complicated with the Greater White-toothed Shrew, where the species occurs at low densities it has positive effects on Barn Owl productivity and fledging success. However where the species makes up a large part of the Barn Owls diet negative effects have been found. The condition of the chicks, weight and fledging success is reduced in the brood, which can result, in some instances with the entire brood failing. Due to the overlap in ecology of the Barn Owl with both the Kestrel and the Long-eared Owl, similar effects can be anticipated in these two species. It is clear that the present of the Bank Vole and Greater White-toothed Shrew will have a significant influence on the future status of the Kestrel and Long-eared Owl.

Greater-white Toothed Shrew - by John Murphy

The analysis of raptor pellets has pointed to a marked reduction in Pygmy Shrew numbers where the Greater White-toothed Shrew occurs at high densities such as areas of South Tipperary. The theory has been comprehensively verified by Queen’s University small mammal researcher. Their findings demonstrate that the Greater White-toothed Shrew has a positive effect on the Bank Vole, prompting its densities to increase in a given area while affecting local extinction in Pygmy Shrews. The Bank Vole is also seen to gradually replace the Wood Mouse with the effect seen to be reduced the further removed from the point of introduction the community lies.

These two invasive small mammal species are already having top-down and bottom-up effects in terrestrial ecosystems around the country and these will be for the most part negative and will eventually spread across the entire island.    

Research Around the Clock

The morning often sees me trying to track down Kestrel nesting sites and yesterday morning was no different. Between the squalls of a rain laden wind I watched a small shelter belt of conifer and pine which has been a traditional nesting site for Kestrel in the area. The first sign I had of this small falcon’s presence was provided by Rooks. They repeatedly dive bombed, with angry swoops on an area at the centre of the shelter belt. This kind of behaviour is reserved by most birds for predators. It is both a clear statement to the predator that they have been seen and an attempt to drive them away. It is usually performed by a group of birds. Looking for this type of behaviour has become such a habit that the everyday alarm calls^* of a Blackbird or Swallow demand of me, my immediate attention.

Happily the Rooks had done my work for me by finding the Kestrels. There was a pair on site and it wasn’t long before the female returned to her nest. This latest find brings the total of Kestrel pairs found in the West Offaly area to ten, a good number but I am still hopeful that I will find more. Should anyone have information on the location of a nest do be sure to get in touch.

After lunch it’s time to do some Barn Owl, and Kestrel, nest monitoring. These visits aim to record productivity, the relative health of the broods and to ring the chicks. Tuesday, just gone, produced some great numbers. A ruin just outside Banagher played host to six Kestrel chicks and three Barn Owl chicks; all of which were in good health and should all fledge without difficulty. This brood of six represents the largest brood of Kestrels in the country (pictured above). The Barn Owls (pictured below, patiently await us to take their measurements) are quite early, their health and the sheer weight of numbers of Kestrels in the building pay tribute to the rich hunting grounds which the nearby Shannon Callows provides. Another building, close to Tullamore, which has also been a traditional host to both Kestrel and Barn Owls, rounded off the day in some style. We found to our wonder that the Barn Owl nest contained eight eggs. The most BirdWatch Ireland staff have ever seen before in one clutch was six.

The late evening and night of late have seen me carrying out the first phase of a Long-eared Owl chick survey. Monday night saw the completion of phase one. The area surrounding Banagher has proved the most profitable in my search for the calls of young Long-eared Owls (pictured below). I have found three broods within this 10km square but the search will be conducted twice more. It is hoped these later searches will turn up more active sites. Although owls are the marquee nocturnal avian species, they are by no means alone in their nocturnal tendencies. My midnight countryside forays have opened my eyes to the quality of the night time chorus. Grasshopper and Sedge Warblers, Cuckoos, Snipe and Woodcock all broadcast their territorial claims at night. Sadly the afterhour’s cacophonous reel of the Corncrake is now rarely heard in the midlands of Ireland. The summer floods, of a few years past, washed out the nests of this ground nesting bird in the region.

Please do continue to keep in touch with the blog for more avian observations and pictures in the coming weeks as Barn Owls will increasingly be the focus of the project.    

* Interestingly on the subject of alarm calls, there is a bird in Southern Africa called the Fork-tailed Drongo who has learned to mimic the alarm calls of all its neighbours. Drongos watch and wait for a bird to find a tasty morsel, at which point they produce the alarm call of the species in question. The bird instantly flies up in alarm to shelter, leaving behind an easy meal for the Drongo.  

         Barn Owls footage from a Nest Box in south Tipperary

          A big thank you to Brian Dillion for providing the footage and helping out the project

(the footage was collected under licence from the National Parks and Wildlife Service)

This is footage of the female of the pair, who you can see is clearly rung.

                           This is footage of the pair early in the year prior to laying.

This is footage from late April of the first Barn Owl chicks of the season.  

                              

Chick Ringing

I spent all of yesterday with John Lusby, my line manager at BirdWatch Ireland, visiting all of our known West Offaly Kestrel and Long-eared Owl nests. We were monitoring the nests both to record the productivity of each brood and also to ring any chicks that were large enough to do so. To save on a lot of unnecessary ladder and rope play we brought with us a nice new piece of kit. A nest inspection device, and what this effectively is, is a camera on top of a long pole. With all the subtleties of motion which we could summon, we maneuvered our 10m long nest inspection device into position in the hope of an illuminating view of the nest contents. All active nests at this time of year for both Kestrels and Long-eared Owls will have either eggs or chicks. Counting the downy chicks from the picture provided on the small screen of the camera can be a bewildering prospect. At first glance you are faced with a downy mess, of a nondescript nature, but gradually you begin to notice the border lines which separate individuals. Should the chicks be large enough to ring, phase two of the operation begins. The pictures below, in the order in which they appear are a Kestrel chick, Long-eared Owl chick and a close up of the amazing eyes of the same.

A ladder and/or a rope are used to reach the chicks in their lofty nests. In the case of a building a ladder is used and the operation becomes a more straight forward procedure. In the case of the nest being positioned in the extremities of a large tree, John our resident arboreal expert is called into play. Firstly John shots a guide line up into the top most branches which creates an anchor point, which will support his weight while he climbs. Using a maze of knots, a pulley system and not an inconsiderable amount of industry, the tree is climbed and the chicks ringed. Along with the ring number the bird’s age, health and place of birth are recorded.

As these chicks fledge and inevitably disperse, future encounters with them (thanks to the rings), will help to lessen the vale of ignorance which surrounds the lives of these enigmatic birds of prey.  

The Musical Owl

Really nice to have a little warmth in the sun yesterday, the night itself too didn’t have the usual chill factor. I was out on the night shift last night looking for Long-eared Owls. More specifically I was out listening for Long-eared Owl chicks calling (pictured below by John Lusby). The books describe their begging calls to their parents as akin to the sound of a rusty gate squeaking.  This rusty gate analogy for me doesn't fit. Their calls are not at all a sound which would make you wince. The Long-eared Owl chick’s begging is a single, pleasant, drawn out note which seems to somehow fit naturally into the summer night’s soundtrack. The sound doesn't demand your attention but once you’re listening for it the high pitched notes are unmistakable.

The birds which I visited last night are resident on the edge of a rookery. I couldn’t see the nest itself in the nighttime gloom blow a Scots Pine stand but the chicks are not at all shy. I didn't see the chicks either, but standing below the tree they could be easily pinned down to a branch or two from their calls alone. The sound too really travels, I could hear the chicks from at least a kilometer away. I gathered from their chorus, that there were three chicks. One at least has fledged and called from a tree some 30m away. Young Long-eared Owls fledge early, leaving the nest while still flightless and covered in down. This behaviour is thought to be a defence mechanism to guard against predation on the nest. If any of the nestlings are to be ringed, we’ll have to visit the nest site soon before the two remaining chicks have fledged. 

The weather seems to be on the up for the next week at least so why not get out for an evening stroll, and who knows maybe a harmony of Long-eared Owl chicks are playing a wood near you!

Out With the Old in With the New

Last Friday evening I undertook a roost watch at an old castle, which is set in an idyllic area of farmland surrounded by encircling broad leaf woodland. The building is quite well preserved, it lacks a roof but its bell tower and thick buttressed walls remain intact. It must have supported a large community of people in times past, with its many rooms and network of passages. However its present day residences are of an entirely different sort. The building plays host to a large and healthy population of Jackdaws, a pair of Ravens (pictured second below by Stephen McAvoy) and a pair each of Kestrels and Barn Owls (pictured first below by Andrew Kelly). Swifts and Starling complete the list of amorous breeding inhabitants.

I arrived at 20:20 which is an hour before sunset, in the hope of catching sight of the Kestrels before I entered the castle to find the Barn Owl nest site. Happily the Kestrels were not feeling particularly shy, and on arrival the male bird roosted passively on a castle drain pipe for some twenty minutes before heading off to hunt. While I waited for his return, the ravens entertained me with their antics. They wheeled and circled, periodically herding and scattering the Jackdaws of the castle. The sun had set and it was near dark before I had sight or sound of the male Kestrel again. He flew in and resettled himself on his earlier perch and was joined by his mate. Even in the shaded light of this chilly evening the sexes could easily be told apart by size alone. As is common for many raptors the female is the larger of the two. The female finally showed me what I had come to see, her nest entrance just as the light was near fully gone. She flew lightly from her window ledge perch to an arrow slit widow and disappeared from view to resume her incubation of this year’s brood. Phase one of the mission of the evening complete I entered the castle.

Buoyant with my earlier success, I didn't have to wait long before I heard the gentle snoring of the female Barn Owl. This snoring is in fact the begging call (young Barn Owls snore too) which stimulates the male to leave to hunt. A snoring female confirms breeding, which meant my evenings work was complete with both nests found. Success!

Hidden Gems

What miserable weather we’re having today, fortunately Thursday of last week was much nicer which allowed me (and a colleague John Lusby) to get out and check some of my known West Offaly Kestrel nest sites. As promised below is a picture of the inside of a Kestrel nest. These striking specked eggs are from a Kestrel nest in an old ruined mansion just outside Banagher village. The female flushed quite quickly on our arrival on site, the only remaining trace of her was a single moulted feather. Not altogether untypically she remained quite close, often circling overhead, keeping a close watch on proceedings. We were in and out in no time, which happily allowed the female to soon return to her precious six strong clutch. Six is the maximum number of eggs which has been recorded by Birdwatch Ireland at a Kestrel nest. This nest fledged five birds last year, so hopefully similar success is in store in the weeks and months to come.

Although the majority of Kestrel nests which we visited on Thursday were on eggs, there is however quite a degree of variation in timing between pairs. Another site just outside Ferbane hosts a pair who haven't settled down to it yet. The birds are still soaring around their castle abode, a courtship behaviour usually seen earlier in the season. Another pair close by, which I spend a morning with in order to pin down their nest, spent a three hour period copulating and courting. A degree of variation in timing of breeding is natural in a population, with younger birds often being the last to settle down to breed.    

Spring has sprung for most other species and is wearing on, into a hopeful summer. This Chaffinch brood for example, pictured below will be fledging any day now. The nest is perfectly camouflaged at the centre of this Hawthorn bush. The young birds pleads’ for food, being the only clue to their presence. Their industrious parents scolded me angrily, as I took this picture. Continue to keep an eye on the blog for more updates and pictures as the breeding season kicks into overdrive in the coming weeks.

The Windhovers!

The Kestrel is Ireland’s most commonly seen raptor species, it is the only bird of its size (being roughly comparable in size with our cities feral pigeons) to hover and it is most often observed doing just this along motorways. Hunting in this manner, Kestrels are searching for small mammals which make up the vast majority of their diet. To aid them in this search, Kestrels have evolved an extraordinary means by which to track their prey. Kestrels can see in near ultraviolet light. In ultraviolet light the urine droplets which rodents use to mark their territories shine in sunlight, this territorial practice thereby unwittingly drawing their predator upon them. Although this species is widespread and commonly seen, its population is declining in the state, which has increased fears for the health of the wider ecosystem*.

Yesterday May 1^st, was the first day of the project's vantage point survey for Kestrels within the 10km square encompassing Ferbane (IN12). Vantage point surveys are designed to record the flight activity patterns of birds. This method is commonly used to assess the possible impact of a wind farm on a bird community. Vantage point surveying is often a prerequisite before planning permission can be awarded to such industries. In my case however, I am interested in breeding densities of Kestrels in the area. It is hoped by recording the activities of Kestrels, activity ‘hot spots’ will come to light. The activity ‘hot spots’ will then be used to establish the number of breeding territories in the locality. Unfortunately high ground is at a minimum around Ferbane. The area is quit flat, with a patchwork of fields encircled with mature hedgerows. Although this will make vantage point surveying more difficult, it does however make for very pleasant surroundings in which to work.

There are six known, to BirdWatch Ireland (BWI), Kestrel breeding sites in West Offaly. This number cannot in reality represent the true number of breeding birds in the area, it is for this reason that I reiterate my appeal for any sighting to be reported to BWI.  Kestrel nest in a variety of different sites, ranging from old corvid nests in trees to ledges in abandoned buildings. The above pictures show an old castle from the outside and the second picture shows the inside where the nest site is located on the top shelf. The six active sites are in full swing. The males are making frequent visits to nests, to supply their sitting mates with food and support. One instance, on visiting a Kestrel nest in a monkey puzzle tree, I saw the male bird’s defensive abilities in full effect. He repeatedly dive bombed a Hooded Crow who was loitering in the locality of the tree. Given the Hooded Crow’s reputation for egg robbery, this intervention seemed particularly necessary. Kestrel females will generally be on broods of 4-6 eggs at present which they will brood typically for around a month. Both parents will then provision the resulting chicks for a further month before fledging. It is hoped that we will revisit each of these nests in this period before fledging to ring the chicks. Ringing helps in establishing survival and dispersal rates of young birds.

To further help breeding Kestrels in West Offaly, a nest box scheme will be rolled out later this summer. The boxes are being built by the local secondary school Banagher College and Tus. The boxes are useful on two fronts both as a conservation measure and they also make monitoring nest sites easier. This is a really important part of the project and I can’t thank Tus (myself and two of the Tus works below) and Banagher College enough.

The project will be concentrating on surveying for Kestrels during May. Keep an eye on the blog in the coming weeks for pictures of some of the Kestrel nests I will be visiting. Also Kestrels will be very active this month, keep an eye out for males carrying prey in their talons, this is a sure sign that Kestrels are breeding in your area.

     

*The Kestrel Falco tinnunculus is a top avian predator of the wider countryside, and as such is an excellent sentinel of environmental health. Pollutants in the environment are most strongly felt by top predators. The Kestrel has a widespread distribution throughout Europe, it is listed as a Species of European Conservation concern (SPEC 3). In Ireland the Kestrel population has declined by 15% between the first Breeding Atlas (1968-1972) and the New Breeding Atlas (1988-1991). The Irish population is on the Amber list of the Birds of Conservation Concern in Ireland. Factors previously implicated in the Kestrels decline are agricultural intensification leading to the loss of suitable foraging habitat, the loss of nest sites and climate change. 

Territorial Owls Give the Game Away

Long-Eared Owls (pictured below by Richard T. Mills) are rarely, if ever seen. They are nocturnal, have cryptic plumage and a secretive nature. How then does one survey for the presence or absence of breeding individuals? Previous studies have relied on late summer visits, to likely nesting habitat, after dark to listen out for the begging calls of young Long-Eared Owls. The calls are described as, akin to the sound of a rusty gate closing. Using this technique, however, failed breeders are over looked. To overcome this The Raptor Conservation Project of BWI has rolled out a playback survey. This will represent the first such undertaking in the state.

The survey aims to establish breeding densities of both successful and unsuccessful pairs of Long-Eared Owls within the 10km squares surrounding the West Offaly towns of Banagher, Ferbane and Belmont (IN01, IN12 and IN02 respectively). This project also aims to assess the effectiveness of the playback technique in Ireland and to provide data on the ecological requirements of the species.

What exactly is a playback survey? The concept itself is not a new one it is used in many parts of the world, for many different and contrasting species. In essence the technique relies on the territorial nature of many species. Raptors particularly can have strong territorial tendencies. By broadcasting the calls of a con-specific, a member of its own species, it is hoped that any resident birds will respond with a corresponding call or noise of some sort. This technique finds its true value for elusive species such as our study species the Long-Eared Owl. In practise I visited each accessible 1km square, of each of the 10km squares and broadcast Long-Eared Owl calls as close as possible to the centre of each (I undertook this survey under licence from the National Parks and Wildlife Service and with the use of best scientific practices). Responses varied from one coo (the male call) to a full blown aerial barrage of coos and wing claps circling over head (a territorial behaviour of males). Females also responded, on occasion, producing a nasal sounding call.

By revisiting each of the 10km squares in late summer to listening for the begging callings of young Long-Eared Owls (below), comparisons can be made to calculate the effectiveness of this playback technique. Success with this technique for surveying Long-Eared Owls in West Offaly could prove of great importance in assessing the national population of the species.

Barn Owl Survey

This survey aims to establish breeding densities of Barn Owls across three 10km² areas in West Offaly. The squares selected for this survey are, IN 01 which encompasses Banagher and its surrounding town lands, IN 02 which has Belmont as its centre and IN 12 which has Boora Parklands just to its south and Ferbane in the west of the square. Results from this strategic survey, along with that of a mirrored project being undertaken by my colleague Michael O’Clery in Duhallow¹, are hoped to provide inference as to the national population of breeding Barn Owls in Ireland.

Specifically, how does one survey for Barn Owls?

Each 10km square is surveyed individually, by travelling across the square and assessing all building’s suitability for Barn Owl nests. Although Barn Owls do on occasion nest in tree cavities, it was deemed unfeasible to survey trees for the purposes of this survey; an account of this will be taken in the final analysis. A suitable building for a Barn Owl must at a minimum provide a cavity for the nest site and have low levels of disturbance. This is most often found in ruined buildings where an old Jackdaw’s nest provides a platform within the chimney (Barn Owls pictured in a chimney below). Other favoured sites are crevices which provide access to a wall cavity in a ruined castle or mansion house.

Having at this point eliminated all unlikely buildings, promising buildings are now surveyed in detail; with permission to enter received from the owner. Likely buildings are meticulously searched for any and all evidence of Barn Owl activity. Any chimneys on site are examined for the presence of old Jackdaw nests, the interior and exterior walls are inspected for white washing (this can look like drops of white paint on the walls) and the property is scrutinised for pellets (Barn Owl pellets pictured below). Pellets are regurgitated hair and bone fragments which the owls cannot digest². If fresh pellets are found in the building it is flagged as potentially active and a roost watch is undertaken. All suitable buildings, however, even if found unoccupied, are recorded; thereby quantifying nest site availability within each 10km square.  

As Kestrels, Peregrine Falcons, Ravens and Jackdaw all frequent similar haunts, any of these species found on site are also recorded. Given the inaccessibility of Barn Owl nests predation is unusual, however, Pine Martens can access nests and, as such, evidence of their presence is also recorded for predation risk models.  

^1. John Lusby, Raptor Conservation Officer with BirdWatch Ireland said “Duhallow, which is an area encompassing parts of North Cork and East Kerry seems to be particularly suitable for Barn Owls, the local population appears to be doing well here and we have recorded one of the highest known densities of nest and roost sites in the country. Given the fact that Barn Owls have declined so markedly in other parts of the country, areas such as this are crucial for the conservation of the national population”

^2. These pellets provide an invaluable insight into the diet of Barn Owls. Individual bone fragments can be identified and a catalogue then created of the species on which the owls prey. In 2008 a discovery of some interest was found in Barn Owl pellets in Co. Limerick. A previously unheralded alien species, the White-toothed Shrew was discovered through pellet analysis to be resident in the locality.

Raptor Study Underway

West Offaly is to host a detailed raptor survey over the coming months. This BirdWatch Ireland project has been funded by Banagher Local Development Company in collaboration Banagher Tidy Towns through the LEADER 2009-2013 programme. The project aims to establish breeding densities of three raptor species in the area. Barn Owls, Long Eared Owls and Kestrels have not been studied in such detail in the area and the results will provide invaluable insights into the current status of the three species nationally. John Lusby BirdWatch Ireland Raptor Conservation Officer stated “despite the fact that these raptors are still widespread and relatively common there have been virtually no specific studies on these species in Ireland, and as a result we are lacking information on even basic aspects of their ecology”. Specifically the project will aim to locate nest sites for the three species and monitor the success of any breeding attempts. A nest box programme will also be rolled out to provide additional nest sites and to aid monitoring.

Until quite recently our knowledge of Barn Owls in Ireland had been relatively limited. The elusive nature of this iconic species meant that it was extremely difficult to gain an overview of the issues that impacted upon these owls. Thankfully this situation has changed dramatically over the past five years largely due to the tireless efforts of volunteers who have facilitated the comprehensive monitoring of Barn Owl populations throughout the country. As a result of their hard work, co-ordinated by the Raptor Conservation Project, we now have a much better understanding of the ecological requirements of our Barn Owls and the factors which affect their conservation status. The success of this project has provided a blueprint for current undertakings.

West Offaly is ideally suited to a raptor monitoring scheme owing to its unique ecosystems, with particular reference to the Shannon Callows and the restored bog of Boora Parklands. The locality supports a wealth of biodiversity including a healthy raptor population. Although West Offaly is well known for the beauty of its landscapes and wildlife this project aims to further encourage an active and meaningful engagement with wildlife. The aims of the project will be achieved through four individual project components, each of which are interlinked and feed into one another.   

Detailed survey work will be carried out within specially selected areas within West Offaly and aims to identify roost and nest sites for Barn Owls, Long-Eared Owls and Kestrels in order to establish breeding density in the region. The public are encouraged to help by contacting BirdWatch Ireland with sightings of any of these key species. Posters detailing the project with relevant contacts will be circulated where appropriate. The farming community in particular are encouraged to participate given their invaluable knowledge of the local countryside. Nests that are discovered will be monitored and chicks will be ringed under license from the National Parks and Wildlife Service.

A nest box and basket scheme will also be rolled out for the three species. The provision of nest sites provides a tangible management system by which local raptor population can be conserved. Nest boxes and baskets provide a safe, secure nest site in areas of suitable habitat where natural sites may be limited. Local groups will construct 20 nest boxes for Kestrels and Barn Owls and 10 baskets for Long-Eared Owls. The work of these groups will prove to be a great help to future monitoring and conservation efforts for Barn Owls, Long-Eared Owls and Kestrels in West Offaly. Previously carried out survey work will highlight suitable locations where artificial nest sites can be placed.

Another exciting element of the project will the use nest camera both for research purposes and to provide the local community with a window into the world of breeding raptor. It is hoped that everything from incubation, the subsequent hatching and rearing will be caught on camera. It is hoped that the system will provide live footage on the internet. It is purposed that this element of the project will be rolled out in 2013.

All questions on the project or sightings of Barn Owls, Long-Eared Owls and Kestrels can be directed to Padraig Cregg by email at pcregg@birdwatchireland.ie or by phone at 087 7866357.