Great British weather (28 August 2007)

It is often joked that Britain does not have a climate; we just have lots of weather. The period from April to August 2007 has borne this out. April was very warm, with mean temperatures about 3ºC above normal, and dry, only 3 or 4 days having any rainfall. Then, May to July was the wettest in England since records began, in 1766. The map, published by the UK Meteorological Office (http://www.metoffice.gov.uk/corporate/pressoffice/2007/pr20070726.html) shows that much of England received from two to three times the average rainfall during the twelve-week period from 1 May to 22 July.

The effect on birds has varied from species to species. We have to await full collation of figures, but in general resident birds got away to an early start and many chicks were fledged during April and early May. In the May to July period, temperatures were around normal but any chicks exposed to the rain are likely to have chilled. Adults in open nests must have been torn between brooding chicks, to keep the rain off, and finding food for them.

Thrushes seem to have enjoyed themselves throughout, with easy pickings from worms coming to the surface every time it rained, and multiple breeding attempts. Robins, making well-sheltered nests and feeding on the ground, also seem to have flourished.

Many insectivorous birds, however, have had a tough time. The woodland hole-nesters, tits and flycatchers, found many of their caterpillar prey washed out of the tree-canopy and many chicks starved. Warblers seem to have had varied success, with Locustella and Acrocephalus species faring badly, and the woodland/ hedgerow Sylvia and Phylloscopus species, on average, coping.

Most finches and corvids appear to have bred normally.

Apart from much reduced numbers of some species, others have delayed moult and tried to have a late brood.

The sporadic feeding conditions are also indicated by ringers seeing far more birds than usual with fault bars.

There are thus, compared to a normal year, more adults that are moulting late, and more first-year birds with poor quality feathers. Both of those factors would suggest that mortality will be higher than normal during the coming months.

An adult (Euring code 6, after-second-year) male Goldfinch caught on 10 April 2007 had plumage in almost perfect condition:

On the other hand, another bird caught at the same time - easily identifiable as Euring code 5 (second-year) by the moult limit in its wing (1 old greater covert) and the shape of its tail feathers - showed much more abrasion. Wear is always especially noticeable on the lighter-coloured parts of the most exposed feathers, in this case the tips of the tertials and tail, where almost all of the white parts of the feathers have worn away:

All of the cardueline finches usually breed late. According to the BTO's Breeding Birds in the Wider Countryside (http://www.bto.org/birdtrends2006/wcrgoldf.htm) the median first-egg date for Goldfinch is 1 June. The following bird, ringed on 24 August 2007, must have come from a much earlier nest as it had almost finished its post-juvenile moult:

Its wing and tail make an interesting contrast to the bird from April (above). This individual has also retained 1 old greater covert. As in the image of the April bird, the 9th (counting descendently) and the minute outermost primaries are not visible, hidden behind the 8th primary.

These two Blackcaps Sylvia atricapilla, ringed at the same time on 25 August 2007, illustrate the extremes of early and late broods. They are both first-year males. The bird on the left still has most of its juvenile plumage, loose and fluffy, and is obviously moulting its juvenile head feathers; the bird on the right is fully in post-juvenile plumage with tight, sleek body feathers and a fully black cap:

The Robin Erithacus rubecula depicted next is the product of a late nest. It had only just started to moult out of its spotty juvenile plumage when ringed on 24 August 2007. At the same time, many other first-year Robins already have completed their post-juvenile moult.

This male Blackcap, ringed on 25 August 2007, set an interesting test for the unwary. It is an adult, just finishing its full moult and still growing its innermost two secondaries. The primaries and tail were all fully grown. With an average primary moult duration of around 50 days (Moult in Birds, H B Ginn and D S Melville, BTO Guide 19), this bird must have started moulting in early July and thus must have finished breeding after a successful early brood, or else it failed and did not re-nest.

Whitethroats Sylvia communis quite often seem to moult the outermost tail feathers as part of their post-juvenile moult, growing an adult-type rectrix in the process. This bird, ringed on 20 August 2007, had moulted just r6 on its left-hand side only. There is a striking difference in colour - pure white against the dingy brownish white of the first-year feather - and wear, with a more subtle distinction in shape of the feather tip.

A first-year Blackcap had also, presumably accidentally, moulted just one tail feather, r4 on its right-hand side, which was still growing when the bird was ringed on 25 August 2007. Here the difference in colour, wear and shape is much more difficult to discern:

House Sparrow chicks grow remarkably poor-quality feathers in the nest, presumably the reason why they have a complete moult starting a few weeks after they fledge. The following bird, ringed on 13 August 2007, has striations across many feathers, probably caused by ectoparasites such as mites. It had already lost the tips of most of its rectrices.

Sedge Warbler Acrocephalus schoenobaenus is one of the species notorious for exhibiting growth bars; this bird, ringed on 24 August 2007, is typical:

Bullfinch Pyrrhula pyrrhula is amongst the last of all passerines to breed. The young bird depicted below, ringed on 25 August 2007, has just started its post-juvenile moult and can be sexed as a male by the pinkish-red body feathers just starting to emerge on its breast. A similar bird with emerging female breast feathers was depicted here.

Lesser Whitethroats Sylvia curruca are prized birds in Merseyside Ringing Group, so we need little excuse to take photographs. This first-year bird was ringed on 20 August 2007 at Oxmoor Local Nature Reserve, only the second ever caught there.

It had a more obvious moult limit, with 1 retained old greater covert, than any Lesser Whitethroat that I have ever seen before.

The plumage of adult Reed Warblers Acrocephalus scirpaceus appears to be amongst the most worn of any passerine seen in Britain. This is nothing to do with the British weather but is presumably because they spend much of the breeding season brushing through phragmites reed beds.

This adult bird appears to have moulted its innermost three secondaries later than the rest of its wing feathers. They are noticeably longer and are much less worn than the other three secondary feathers, despite their extra length making them more exposed. This was symmetrical on both wings, and therefore unlikely to be the result of an accident.

Svensson's Identification Guide to European Passerines (1992) encodes the moult strategy, for adults and young birds, as

sp, WC [or:] sp, W₁C, w₂p.

For those not familiar with the coding system, this means that they have a summer partial moult and a winter complete moult; or, an early winter complete moult and a late winter partial moult. The late winter partial moult is normally of body feathers and wing-coverts, but I wonder if this bird also moulted those three secondaries then. For comparison, the following is the wing of a 'normal' Reed Warbler, albeit another bird having secondaries with somewhat irregular lengths.

Reed Warbler appears to be one of the species whose breeding in 2007 has been most severely hit by the wet weather. Our catch totals of first-year birds are less than half of their normal levels.

I have commented previously that Jackdaws Corvus monedula are wary birds, and one in a mist-net on 10 April was a surprise. It was an adult female (with a developing brood patch), aged as Euring code 6 (after-second-year) partly by its very broad, truncate, tail feathers.

David Norman.