Autumn bird migration news: Full of eastern promise
Each week Paul and Nick from the BTO are updating us on all the comings and goings of autumn's bird migration. We'd love to hear what you've been seeing too, whether in your garden or out and about.
The hawfinch, arriving this week © Edmund Fellowes/BTO
Strong westerly winds have dominated the weather this week. As a consequence songbird migration has been very slow. The strong winds did, however, blow Leach's petrels into coastal waters along the west coast. Reasonable numbers were seen at several locations - particularly in the northwest - over the weekend.
When the wind has dropped slightly birds have taken the opportunity to move. With the majority of the swallows having left already it's been the finches that have been the most obvious and of these the goldfinch has lead the way, 1,325 moved south over Spurn in East Yorkshire, on Monday.
The fieldfare: a herald of autumn © John Harding/BTO
These finch movements have included a smaller number of linnets, redpolls, siskins, the first few bramblings and, of particular note, crossbills and a handful of hawfinches. Judging by the rise in the number of these birds spotted on the east coast, these are like to have an origin further north and east of the UK. [Editor's note: Autumnwatch was at Spurn in full force earlier this week. Watch Friday's show to see why it's such a Mecca for bird lovers.]
House martins now dominate the hirundine movement. As the winds drop over the next few days we should see a big exodus of this species.
The last few days has also seen the arrival of more redwings and a smaller number of fieldfares. No doubt this is a result of the conditions that also brought the hawfinches and crossbills. The thrushes have been very quick to push inland and many counties have recorded their first of the autumn in the last few days.
What to look out for this weekend
The wind is due to turn south and southeasterly over the weekend. While it will be moderate in the south, it's going to be quite strong in the north. This will mean that it could be quiet few days on the wildfowl front but we could see the first large influx of winter thrushes, goldcrests and the first movement of woodcock, particularly on the east coast.
Question of the week: Why do birds sing in autumn?
It might seem illogical for birds to sing in autumn; after all, very few of our songbirds will be nest- building or egg-laying over the next four months or so, so why would males bother trying to attract attention now? There are, however, some interesting ecological and physiological explanations.
Why do robins sing in the autumn? © Jill Pakenham/BTO
Some species, like robins, sing to establish and defend winter territories. This ensures that individuals have somewhere to feed during the difficult months ahead, and are in the best possible condition come the start of the breeding season. From a physiological perspective, it seems that the post-breeding moult of some of our songbirds, such as starlings, causes increased testosterone levels, which may in turn trigger autumnal singing.
This effectively means that autumn is the start of the breeding season for these species, but inclement weather and shortening day-length then suppress further breeding activity until spring. Research into autumn-singing robins, however, suggests that their testosterone levels are not particularly high at this time of year, so testosterone is not the only answer. Furthermore, autumn robin song is quieter and of a different quality to that of spring.
A number of migratory and flocking species also sing in the autumn. There is even some evidence that female and juvenile birds of some migratory species also sing at this time. One possible explanation is that these birds are singing to maintain social status within the flock. A weak, quiet song, termed 'subsong', can also be given by lone migrants; its role isn't entirely clear but could be part of the song-learning process for young males, prior to their first breeding season the following spring.
Have you noticed any birds leaving yet? Anything unusual or surprising? As always, we'd love to hear, so post a comment below.