Tuesday, 7 December 2010

Yet more hard weather

Another battle to get in and out from work in Edinburgh on Tuesday, with some backroads virtually impassable and snow still lying to 40cm at the nursery in Gilmerton. Min temp at Edinburgh airport -16C, so all snow frozen solid and ice everywhere.

Not much time for birds but noted first report coming in of Red Grouse incursion to lowlands (Haddington), reminiscent of the widespread influx earlier in the year (see map, though several reports have not (yet) been submitted to the atlas); this follows recent reports of higher numbers in peripheral areas in Borders (Greenlaw, Eildon, Gordon) and as per the severe weather last winter the relative lack of wind may well be a major contributory factor - snow is lying deep and has not been blown off vegetation. On the other hand, a lack of wind might help owls, seeking prey by sound, and they need all the help they can get right now.

Wednesday morning still perishingly cold, 25 Waxwings seen off by a Mistle Thrush at rowan in Forthview Road, Longniddry.

Wednesday evening en route home at 17:20hrs, one of my saddest observations as a birder, under the A1 bridge at Old Craighall where the Feral Pigeons nest and roost, a Barn Owl down on the road at a pigeon. Stopped and recovered the owl, it had been struck but was still alive, the pigeon also was warm but the neck had been eaten; initial hypothesis was that in the continuing sub-zero temperatures, with snow still lying deep in all surrounding areas, the owl had gone to the pigeon roost in search of food and successfully taken a pigeon there. Possibly taken in flight or pigeon killed on the ledges below the bridge and then dropped to the road surface below. In great hunger owl immediately began to scavenge the pigeon where it lay on the road and with cars passing at two or three every minute it would soon have been dazzled then struck on the road, only the face (and feet, where presumed gripping prey) had visible blood. This must have happened within a couple of minutes of my arrival as the bird flapped when I took it into the car, but I had to lie it down and it did not move again.

More careful examination at 19:00hrs showed owl still quite warm and body flexible but pigeon now stiff and barely warm, so change of hypothesis to pigeon being an earlier road casualty, and owl scavenging. Later at 20:50hrs the owl was in a similar condition to the pigeon as first found thus supporting conclusion that the pigeon was a fresh road casualty from early afternoon, c. 14:30hrs, at least prior to going to roost and before the owl was likely out, and thus it had been discovered later. If this were the case it would be of interest as scavenging is virtually unknown in Barn Owl, just one mention in BWP (Dunsire, C & Dunsire, R (1978) "Barn Owl on dead Hedgehog", Scottish Birds, 10, 56). Will send both birds to vet for post mortem and this may confirm cause of death of pigeon. Also weighed owl, 285g, on the light side (especially if female, as spots suggest, mean winter is 313g, male 298g), but still above starvation weights (one from Borders dead in shed was 233g, another local casualty in poor condition was 247g, BWP gives starvation weights as 220g, n=33, max 248g).

A quick search of literature for observations of Barn Owls at carrion, or on road surface reveals some interesting comments on Barn Owl Trust report, "Barn Owls and Major Roads" (pdf). A sighting of a Barn Owl standing in a road perched on a road casualty Hedgehog Erinaceus europaeus is mentioned (Mikkola, H (1983) "Owls of Europe", Calton: T & AD Poyser) but this is presumably derived from the same Dunsire report above. Approx 10 other reports in several thousand observations of the species standing on road surface. From my own observations, one record of owl on the B6363 just south of Longniddry, sitting in middle of road at 03:44hrs on 23/04/06, in a few 10s of live sightings here, so perhaps it is not quite as rare as suggested. Have seen this more than once from Tawny Owl, though one such case may have been a stunned bird.

My son, age 4, was sad too and commented: "Bloomin person drive right over a owl; but owls are very nice" (i.e. people should be careful not to hit them).

Thursday George tells me of another Barn Owl casualty on A1, by Torness (recovered and is unringed) - last year's pattern is repeating and again we find relevant info in the Barn Owl Trust report which discusses (under A.16) the reasons advanced by Newton et al. (1991) relating poor condition (which may correlate to hard weather) and a) spending longer hunting, b) hunting in places where accidents more likely or c) being less able to avoid collisions. Whilst the overall results of Barn Owl mortality studies, also found thus far in Lothian, is that many casualties are in excellent condition, and overall no worse than average, a focus on severe weather cases may give a different result?

Friday morning, 817 Greylags at potatoes at East Fortune (where I recovered my mobile phone, frozen in the snow since Sunday!).

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