First Barn Owl chicks of the year make an appearance

Although it has been a relatively slow start to the spring for most raptors, Barn Owl chicks have made an appearance at a site in Co. Limerick, the first of the season.

An evocative place - a ruined castle, a full moon, and a nest full of Barn Owls within, calling to be fed, 20th May 2016 (M.O'Clery).

Most Barn Owl sites which have been checked so far indicate that egg-laying and hatching are probably a few weeks later than the average but, at this castle at least, chicks could be heard that were about 10 days old, with others just a few days old. Incubation of Barn Owl eggs is about 30 days, so it looks like this Barn Owl pair set about egg-laying around 20th April. The average laying date for Ireland is about 8th May, though this can vary by three and even four weeks either way in most years.

Results of 2015 National Hen Harrier Survey show declines for Ireland’s skydancer

As one of Ireland’s rarest birds of prey, the long-term declines in Hen Harrier populations provides cause for concern, particularly given the important role this species has to play in our wild and rural landscapes. Hen Harriers are renowned for their spectacular aerial courtship displays known as the ‘skydance’. Traditionally, Hen Harriers breed in open upland habitats, using heather, pre-thicket forest plantations or scrub for nesting while feeding on small birds and mammals. Like many birds of prey, Hen Harriers are a valuable indicator of the health of our countryside. The 2015 National Survey of Hen Harriers (the fourth national survey since 1998-2000) has shown that the national population has experienced further declines, including within some former strongholds for the species.

Female Hen Harrier (Shay Connolly).

The fourth national survey of Hen Harriers in 2015 was undertaken by a partnership of the Golden Eagle Trust, Irish Raptor Study Group and BirdWatch Ireland on behalf of the National Parks and Wildlife Service. Similar to previous surveys the 2015 national survey received enthusiastic support from a substantial network of voluntary surveyors including bird-watchers, farmers, wildlife rangers, foresters and biologists with more than 250 fieldworkers dedicating over 7,000 hours collectively to the survey. This facilitated comprehensive coverage throughout the country and also allowed assessment of new areas not previously surveyed. 

Dr. Marc Ruddock, survey coordinator with Golden Eagle Trust, commented on the efforts involved ‘This is one of the largest surveys of its kind, and would not have been possible without the significant investment of so many skilled surveyors which is nothing short of phenomenal, that so many devoted their time and energy to the survey is hugely positive and demonstrates the passion that is out there to help understand and help conserve Hen Harrier populations in Ireland’. Ruddock continued: ‘to all those involved we extend our considerable thanks and appreciation.’

The current national population estimate of 108-157 breeding pairs in 2015 represents a decline of 8.7% since the 2010 national survey which recorded 128-172 pairs. Due to the increase in survey effort in 2015, the most accurate assessment of national population trends can be calculated through a comparison of Hen Harrier numbers in specific survey squares which were covered across the various national surveys. These results indicate a decline of 16.4% in the national Hen Harrier population since 2010 (based on assessment of Hen Harrier numbers recorded within 139 10km squares surveyed in both 2010 and 2015) and 9.7% declines since 2005 (based on 110 10km squares covered in 2015 and 2005). A comparison of the survey area (78 10km squares) which was covered in all four national surveys (since 1998) indicates that the population has fallen from 110-155 pairs during the first national survey in 1998–2000, compared with 95-130 pairs in 2015, which is an overall decline of approximately one third (-33.5%) over this 15 year period.

Male Hen Harrier (M.O'Clery).

As top predators, the decline of Hen Harriers may be linked with declines in availability of their preferred habitat, changes in habitat quality and associated effects on food availability. It is likely that land-use changes over the past 50 years, which may have resulted in an increasingly fragmented and/or unsuitable landscape for upland breeding birds, may be impacting on the Hen Harrier. Other studies have shown similar declines in upland species such as Curlew and Red Grouse.

In 2007, as a requirement under the EU Birds Directive, Ireland designated six sites as Special Protected Areas (SPAs) based on their national importance for breeding Hen Harriers, including upland areas in counties Clare, Cork, Galway, Kerry, Laois, Limerick, Monaghan, Offaly and Tipperary, which together make up 2.3% of land area in the Republic of Ireland. Management of this SPA network requires that Hen Harrier populations are maintained and enhanced while also being compatible with stakeholder requirements. Supporting farmers and landowners, particularly within SPAs, to manage their lands using traditional and sustainable practices is key to Hen Harrier conservation. 

In 2015, harrier populations in several of the SPA areas were recorded to decline with an overall decline of 26.6% since 2005. Speaking of these trends, John Lusby, survey coordinator with BirdWatch Ireland commented ‘the fact that the SPA network holds 44% of known pairs in the country, which is a significant proportion of the population, shows just how important these areas are in the national context. The current survey results confirm that populations within parts of the SPA network are declining and without intervention through appropriate management further declines at certain sites are anticipated’.

Dr. Allan Mee, survey coordinator with the Irish Raptor Study Group, commented on the specific pressures faced by harrier populations. 'There was a wide range of different pressures recorded in the national survey both within and outside SPAs, and many of these warrant further investigation. Pressures such as forest maturation, clear-felling, wind energy production, agricultural intensification, uncontrolled burning and degradation of important open habitats such as heather moorland, turf cutting, and recreational disturbance were all recorded by observers during the study. Mee continued “It is important to understand why some harrier populations may be declining and thus a comprehensive and scientifically robust action plan is needed to maintain or enhance existing Hen Harrier populations into the future.'

The results of the 2015 national survey will serve to inform the Hen Harrier Threat Response Plan which is currently in preparation through the National Parks and Wildlife Service with input from a wide range of relevant stakeholders. The purpose of this plan is to identify the main threats to Hen Harriers and identify integrated solutions and actions required for a sustainable management of the species. If the plan is successful, it has the potential to deliver an effective framework for conservation of the Hen Harrier and other priority upland birds and habitats.

You can download the PDF of the 2015 National Survey of Breeding Hen Harriers HERE

For further information, contact:

Marc Ruddock, Golden Eagle Trust.   Email: marcruddock@goldeneagle.ie Tel: 087-3578590

Allan Mee, IRSG Chairman.  Email: allanmee@goldeneagle.ie Tel: 087-3117608.



John Lusby, Raptor Conservation Officer, BirdWatch Ireland. Email: jlusby@birdwatchireland.ie

New Shrew spreading fast

A large scale survey of Barn Owls is underway this spring and summer in counties Tipperary, Limerick and north Cork, and in all but one of twenty or so active sites found so far, the pellets of Barn Owls have contained the remains of Greater White-toothed Shrew, a newly discovered invasive species which is spreading rapidly. The implications for birds of prey, and other small mammal species, has the potential to be profound.

Jaw bones of Greater White-toothed Shrew, from a Barn Owl pellet in Tipperary, March 2016. This species is almost three times larger than the native Pygmy Shrew (M.O'Clery).

A collection of jawbones from just one Barn Owl pellet in Tipperary, containing remains of four Greater White-toothed Shrews and one Wood Mouse, lower left (M.O'Clery).

The shrew arrived in Ireland before 2007 possibly around 2004, and by 2013 had spread to occupy an area of 7,600 square kilometres. The source of the invasion has not been established with certainty, though there are a number of large stud farms in the central core area of the shrew, so a possible mechanism for introducing it could have been in the importing of fodder or straw bedding, etc, for the local horse-breeding industry.

Greater White-toothed Shrews (DerHexer, Wikimedia Commons, CC-by-sa 4.0).

In 2012, Greater White-toothed Shrews were calculated to have been spreading at an average rate of 5.5km per year, this rate varying according to local obstructions to its progress such as major rivers, etc. This rate of spread is more than twice that of another invasive mammal, the Bank Vole (estimated to be spreading at 2.5km per year). 

Greater White-toothed Shrews produce up to four litters each year, with litter sizes averaging around seven, and it is the first litter of the year which disperses furthest and is  capable of breeding before the summer is out.

The range of Greater White-toothed Shrews includes most of western Europe - with the exclusion of the Britain - and North Africa, with an introduced population on Las Palmas in the Canary Islands (Wikimedia Commons).

Range expansion of Greater White-toothed Shrews in Ireland, to 2013. The rate of expansion averages 5.5km per year (McDavitt, et al, 2014). 

You can click the map above for closer look.

In the range of the Greater White-toothed Shrew in Ireland, Barn Owls are feasting on them, and they can comprise up to 90% of their diet. Kestrels, Hen Harriers, Long-eared Owls and Buzzards are all likely to be feeding on them, and while the news for raptors at least might initially seem encouraging, there have been some more sinister developments. 

For example, in  areas where nesting Barn Owls coincide with the presence of Greater White-toothed Shrew, the owls were nesting earlier, producing more eggs and larger broods, but in 2012 and 2013, many Barn Owl chicks, fed almost exclusively on Greater White-toothed Shrews, were found to be grossly underweight and often sickly. Whether this was a one-off issue (a parasite, bacteria or other infection) or a more long-term issue now facing Barn Owls is not yet clear.

Greater White-toothed Shrew (Rasback Wikimedia Commons).

Wherever the Greater White-toothed Shrew has spread, records of the native Pygmy Shrew have dropped and then disappeared, judging both from the study of raptor pellets, and from live-trapping. It seems the larger Greater White-toothed Shrew (3x the body mass) is quickly ousting the smaller shrew. Pygmy Shrew has been the only shrew species in Ireland for thousands of years and the speed of the invasion, and the much higher densities which the Greater White-toothed Shrews quickly achieve, means that the Pygmy Shrews have little time to adapt to the new competitor.

Two outlying populations of the Greater White-toothed Shrew have already been found, near Monaghan and on the NW outskirts of Cork City (see map, above), so the rate of spread is likely to increase and it has been calculated it will colonise all of Ireland by 2050. This of course spells disaster for the Pygmy Shrew and it seems it is likely to eventually find refuge only on offshore islands, and possibly peat bogs where it seems to be at a competitive advantage, albeit in low densities. Moreover, where Bank Vole and Greater White-toothed Shrew are found, Wood Mouse numbers have been dropping too.

The long-term effect on raptor populations is uncertain, though there is now nothing to stop the spread of the newcomer. For good or bad, it is here to stay.

A link to the full paper online is HERE.

Citation: McDevitt AD, Montgomery WI, Tosh DG, Lusby J, Reid N, White TA, et al. (2014) Invading and Expanding: Range Dynamics and Ecological Consequences of the Greater White-Toothed Shrew (Crocidura russula) Invasion in Ireland.

A good article on the subject by Michael Viney in the Irish Times can be read HERE.

Barn Owl replacement for road casualty

A visit was made to a Co. Kerry Barn Owl site today, a site where we know a long-lived male was killed on the nearby Tralee Bypass last November. His story is in this post HERE. He used to perch just outside the nest box around this time of year, paying close attention to the female within, hopefully with her about to lay eggs.

And by amazing coincidence, on the exact same beam, almost to the day, just outside the box was a new male Barn Owl, and one that looks like an older bird. Moreover, as you can see in the photo, he is already ringed.

Male Barn Owl, near Tralee, 5th May 2016 (M.O'Clery).

So where might he have come from? Without being able to read the ring, we can't know, but it might be possible to re-trap him this summer. Barn Owls are thought to be sedentary once they have passed their first winter, but if this male is several years old, he might have left another home range to take over at this site, or perhaps he was nearby, unpaired? We are dying to know!

Male Barn Owl, near Tralee, 5th May 2016 (M.O'Clery).