Wednesday, 13 June 2012

Tough Times for Barn Owls

This evening me and Moxey headed out to check some of our Barn Owl nest boxes and revisit a Kestrel and Tawny Owl box and to put things bluntly, the outcome was not positive. Starting with the Barn Owls, we checked a total of six boxes, of the six boxes, five were occupied by adult birds - initially, this was encouraging and to be expected in a 'normal' year. However, on close inspection, of the five nests, only one had any evidence of breeding, with three chicks in the nest. These chicks were too small to ring and we will return in a few weeks, but what was worrying was that the other four nests contained no eggs or young. It is uncommon during nest visits at this time of year to find boxes that are occupied but without any evidence of breeding, so to find four out of six in one evening is worrying and doesn't bode well for a productive breeding season.

Barn Owls came in for a particularly hard time in the post-war years through the use of pesticides and changing farming practices that caused significant damage to the UK population. Long-term nest monitoring data also highlights the importance of the predator-prey relationship that exists between Barn Owls and voles. Vole populations have been shown to be cyclical, peaking every few years with the Barn Owl population showing a similar, delayed pattern.

SWLRG started a nest box monitoring scheme in the 1960's and since then, members of the ringing group have annually monitored the nests and ringed the young. The early signs are that this year is looking like one of the worst years that we have had in recent history and given events like the ritualistic killing of six adult Barn Owls that I reported on a few months ago, this looks like being a tough year for the Barn Owls of SW Lancs. It remains to be seen whether the cause for such a disasterous start to the season can be blamed on the weather, prey populations or disturbance and it could just be a case of a largely delayed breeding season as we are experiencing in some cases with Kestrels this year.

Surviving Kestrel chick

As mentioned earlier, we also checked a Kestrel and a Tawny Owl box. Unfortunately the Tawny Owl had deserted the nest, leaving two cold eggs and this suggests that the eggs were infertile and therefore would never hatch. We did manage to ring one Kestrel at the same location however it was only one chick out of a clutch of five eggs, there was one egg left unhatched meaning that three chicks obviously hadn't made it. With the recent spell of cold, wet and windy weather, it will have been quite difficult for birds to feed and it is likely that the remaining chicks ended up as prey for the largest chick.

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