By Garth Lowe
This has been the fourth year following the progress of known swallow breeding sites in our parishes, and I am extremely grateful to all those kind land owners and householders who have allowed me to continue with my studies. Especially so in this difficult year, with much hardship in our farming community due to Foot & Mouth Disease.
The number of pairs that I monitored last summer dropped to twenty seven, five less than 2000, and seven less than 1999. The previous year was a very productive one, with 198 young fledging compared to only 131 this year. In 1999, 160 young were ringed and eventually fledged. Productivity from pairs seems to be related to weather conditions, this year it averaged out at 5.7/pair, 6.2 in 2000 and only 4.7 in 1999. These figures include the multi-broods they have, and also the failures, through a number of causes.
A recent study in Holland has shown a decline in swallow numbers where the cattle population has dramatically reduced, and there may be a similar effect here.
From a total of fifty-seven adults caught this year, twenty-two had been caught in previous years, giving a good return rate. It is becoming obvious that birds which have bred here before appear to be more successful. In the last two years, at the same location, two pairs had started early enough to have young a week old by the end of May. In one case both adults had bred previously, and in the other just one was an experienced bird. The weather in April and May is quite important for early breeders, on looking back to 1999, there were no young available for ringing until the 6th June, whilst in 2000 and 2001 young were ringed on the 27th May.
Three adults caught again are now all four years old, and have returned to breed at the same location where they were first caught in 1998. This shows just how faithful they are to a site once they have overcome the rigours of migration.
Four birds of this years catch were also first ringed in 1999, three faithfully returned to the same site again each year, but the other, ringed as a nestling down Folly Lane, moved to a stable near the south end of Hopton Lane. It could also have bred here in 2000, as this was the first year birds had nested there, and the site was not monitored then.
Another nestling ringed in 2000 at Brockamin, returned this year to the same farm, and teamed up with an un-ringed female (now ringed). In all the study years very few nestling have returned to the area. This does not necessarily mean they perished: they moved elsewhere to breed, and so keep the gene pool stronger.
There were only three movements from last year, with distances of 0.5, 0.6, and 1.9km. This last bird, a female, from the White House, was obviously courted strongly by a male from Brooklands, near Mousehole, most probably while the swallows were socialising in the air.
Yet another pair returned to exactly to the same nest, and then went on to have three broods, sending eleven youngsters out into the world. Two other pairs also laid clutches of six eggs, instead of the usual five, but only one of them actually reared all six to fledging.
There were two unusual occurrences this year, both worth recording: First, finding a change of pairs in one situation. And, second, catching an extra male at another site. In the first case, by luck I was up a ladder, close to the second nest, when a bird came into feed and perched close enough to see it had no ring. Further catching showed there a completely different pair to the original occupants of the site.
At the second site, on Garway Bank, three birds were caught at the same time. All were previously un-ringed, but catching another, second, male was quite extraordinary. Also strange was the fact that the rightful pair had young around a week old. In 2000 and 1999, the same pair had bred here, but both failed to turn up at this year.
The last young of the year were ringed on 14th September, giving swallows a very long breeding season, but there was a total of twelve young altogether, from four nests, that must have fledged from around the middle to the end of the month. When visiting a nest site in early Oct., I discovered one fledged young, still near the nest, awaiting an adult, which was then observed flying in, probably with food. It does seem that the parental duties can outweigh the call of migration southwards!
A worrying feature was the low productivity this year; if this is repeated elsewhere, there are likely to be a future fall in the number of breeding pairs, when the older birds die, and are not replaced. Next year's study may show whether this has taken place or not!
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