Unusual death of a White-tailed Eagle

Poison was the initial suspected cause of death when a White-tailed Eagle corpse was discovered in Kerry this summer. The cause, it turns out, was very different, and quite unexpected...

Read the article on the Rare Bird Alert website HERE

Moving house – relocation, relocation, relocation

At some Barn Owl nest sites around the country, especially the larger buildings such as derelict mansions and castles, it is not unusual for the adults to switch nest sites from year to year within the same building, or buildings. We are as yet unsure what triggers the switch to alternative nests, but the move can occasionally be forced upon them if the original nest site changes if, for example, Jackdaws fill the cavity with sticks. At other times, there is no obvious reason for the switch. It could also be to do with disturbance, or simply the preference of a new bird, or a mechanism to avoid a build up of parasites at the nest, if viable alternatives are nearby. 

By way of an example, at a large, abandoned farm complex in Co. Kerry, Barn Owls have been nesting for at least six years, though when first detected, they were nesting not in the suitable ruined building but in a cavity in a mature Beech tree adjacent to the buildings. 

Abandoned farm complex in Kerry. The first Barn Owl nest discovered here was not in the eminently suitable ruined buildings, but in the Beech tree just behind from where this photo was taken (M.O’Clery).

Checking the tree nest, from which three chicks fledged (M.O’Clery).

However, by the following summer, the owls had abandoned the tree cavity (it was still apparently suitable) and had instead moved to a section of blocked chimney in the main building.

Left) The second nest, a cavity in the wall with a partially blocked chimney shaft behind and, Right) the third nest site, a nest box in one of the outbuildings nearby (M.O’Clery).

 A nest box was installed in a nearby building, to secure the site in case the chimney became no longer suitable, and the year after that, the owls nested in the nest box. Three moves in three years, but all within 50m.

  

At another location (photo below), again in Co. Kerry, pellets were found under a chimney in a derelict mansion, but careful watching at dusk found there was no nesting taking place in the mansion – the chimney was used only as a roost.  

Derelict mansion in Co. Kerry, an obvious place to start the search for a Barn Owl nest (M.O’Clery).

However, further visits and careful watching at dusk finally located the nest, about 100 m away in the blocked chimney shaft inside a stone outbuilding, a building they shared with a pair of nesting Chough. They successfully raised two young that year, but a visit the following April showed some slates directly over the nest had blown off in winter gales and rain could now fall directly onto the nest, and it had been abandoned. 

The Barn Owl nest was found, not in the mansion, but in the outbuildings, behind the large grey door. (M.O’Clery).

A nest box was quickly made and installed in the outbuilding a few days later and, though there were no signs of owls present, when the box was revisited later that summer, there were three Barn Owl nestlings inside. The adult owls must have discovered the box quickly, because by working out the egg-laying dates from the chicks ages it seems they had moved into the box and laid eggs within about two to three weeks – the fastest uptake of a Barn Owl nest box yet!

Left) John Lusby visits the first nest, an open-topped chimney shaft, covered by a roof. One of the adult owls accessed the nest via the hole in the roof, the other more often flew in through the window and up onto the nest. Right) Once the first nest was rendered useless by missing slates, the owls quickly moved into the nest box placed just a few feet away. (M.O’Clery).

The story doesn’t end there however, because the following year, the nest box was once again empty, so yet again we needed to check the old mansion nearby at dusk and finally it was discovered they had nested that year in an old chimney within the ruin.

Left) The third nest site, arrowed, a cavity in the wall leading from an old fireplace in the derelict mansion. Right, the single chick fledged from this nest in 2015. (M.O’Clery). 

And finally, last summer, yet another evening visit was made to watch and listen at the old fireplace to see if they were nesting there again. Nothing… It was only when leaving the site well after dark that faint ‘snoring’ was heard from young chicks in a high chimney on the other side of the derelict mansion. So in the space of a few years, the owls nested in a chimney shaft in an outbuilding, a nest box in the same outbuilding, a fireplace in the derelict mansion and finally last year, in a high blocked chimney. What will they get up to next?

The fourth nest site, in a vertical chimney shaft in the old mansion (M.O’Clery). 

You can see a short video of the fourth nest at www.vimeo.com/175104175 or use your smart phone to access the video with the VR code above.

There are many other such examples of Barn Owls relocating within the same building, such as at a castle in Duhallow where they switched from a high window ledge to a small wall cavity on the opposite side of the castle, or a site in Kerry where three nest boxes were provided, and they have nested in two so far (and roosted in the third), and a cottage also in Duhallow where they nested in a small roof space in 2013, only to move into the deep blocked chimney in 2014.

So anyone monitoring Barn Owl nest sites and find the original nest empty, keep an open mind, as the owls may simply have relocated nearby.

All Barn Owl ringing and photography at the nest sites  is carried out under licence to NPWS and the BTO.

The great Firies Barn Owl brood of 2015

Ringing of Barn Owl chicks has been undertaken by BirdWatch Ireland since summer 2007, and is providing much valuable insight into their movements and longevity. Around 800 Barn Owls have been ringed, and the recovery rate is relatively high for this species compared with others, for example, about one in ten Barn Owls ringed are re-trapped or recovered (usually dead) at a later stage. For example, for Storm Petrels, this figure is about one in a hundred. Part of it is down to survey and ringing effort, and in part no doubt because of their beauty and rarity (and often their conspicuousness), dead Barn Owls are often reported to BirdWatch Ireland, most often as road casualties.

In total, breeding success has been monitored at over 800 sites in the Republic of Ireland between 2008 and 2016 and in that time 750 owlets were ringed nationally. A total of 74 ringing recoveries and controls (re-trapping of live birds) were recorded between 2008 and 2016. All this accumulating information is proving to be most valuable.

For instance, from the ringing effort in Ireland so far, we know that most young Barn Owls disperse five to about fifty kilometres from their nest site, but occasionally, some will travel much further. The map below shows the ringing recoveries nationally.

Ringing recoveries of Barn Owls in Ireland up to the end of 2015.

However, let’s divert momentarily to a Barn Owl nest site near Firies, in Co. Kerry. 

Cottage in Co. Kerry with three nest boxes. The chimney shaft itself was also a suitable nest site, though the owls never used it (M.)’Clery).

Unusually there are three nest boxes here, one inside the cottage, on in the adjacent barn, and one specially adapted to fit on top of the cottage chimney. This was done in 2009 essentially as an experiment, to see if this might ‘improve’ the nest site for Barn Owls (it certainly did), and to see which nest site might be taken up. Sure enough, Barn Owls moved in that winter and nested the following summer, in the chimney box. 

Left) The chimney nest box on the cottage in Co. Kerry. Right) One of the four chicks at this nest site in 2015 (M.O’Clery).

This has been one of our most productive nests, producing chicks each year since, even in 2014 when breeding success throughout Ireland was extraordinarily low following a record-breaking cold spring. We have ringed chicks at this site for six years now, but the brood of 2016 – four chicks – was to be particularly remarkable.

John Lusby ringed all four chicks on 10th July 2015, and two were subsequently recovered – remarkable in itself that two out of four would be found again - unfortunately both found dead on major roads. The first was killed along a stretch of the M8 in Co. Tipperary, fully 140 km from the nest site, and the second furthest distance recorded by any Barn Owl in Ireland.

The second was found dead on the dual carriageway on 11th February 2017, just NE of Derry. In a straight line this is a distance of just over 350 km, much the longest distance recorded by an Irish Barn Owl and just about doubling the previous record. Of course, the owl had been capable of flying since the previous August, so the distance travelled would be considerably more, and we have no way of knowing what route it took to get to where it met its’ fate.

Thanks to the monitoring and ringing work undertaken at great effort each summer, we are learning much about Barn Owl life histories including their dispersal patterns, distance travelled, and longevity - all vital knowledge in the future conservation of the species.

And while it was remarkable indeed that we recovered two of the four Barn Owls from this nest, and that two of this brood proved to be such long-distance travellers, there is still the intriguing possibility there might be two more from this brood of 2015 out there. Might we yet encounter more of this remarkable family? Wonder where?

All Barn Owl ringing and photography at the nest sites  is carried out under licence to NPWS and the BTO.