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Opportunistic egg predation by Oystercatchers
On 6th March 2007 at Upton Warren nature reserve near Bromsgrove, Worcestershire a pair of Oystercatchers (Haematopus ostralegus) had been feeding with Curlew (Numenius arquata) on an adjacent field. They then flew on to the Flashes where a number of shingle covered island are dotted between two shallow pools.
On one island two pale green duck eggs had been abandoned in the open, about a yard apart, completely exposed and unguarded. One of the Oystercatchers approached an egg and deliberately and without hesitating stabbed it and tried nibbling the contents. The second bird also tried to do the same but between them they managed to roll the egg into the water, where it sank but was still visible. They tried to get it back to the bank but only succeeded in pushing it deeper.
They then turned their attentions to the other egg. The first bird again stabbed the egg and opened its beak forcing a larger hole. It started to eat the contents which could be seen to be fresh with an obvious yellow yolk. The Oystercatcher then picked up the egg using the broken opening and walked towards the waters edge as if to wash it, after the fashion when they catch worms. However the rest of the contents spilled out as both birds tried to eat in the shallows.
This behaviour did not seem experimental but confident and determined with an appearance that it was not the first time they had encountered eggs as a potential food source. Oystercatchers have been recorded previously predating Gull (Larus) and Tern (Sterna) eggs and chicks (BWP) but certainly this is not common behaviour or something I have ever seen before.
Trevor Jones
Birds of the Western Paleartic (1983) Cramp, S. et al Vol 3 pg 22
The eastern-race Chiffchaffs at Kempsey - an update
On the morning of Saturday February 24th I arrived at Kempsey sewage works, in the hope of finally hearing one or both the pale eastern type Chiffchaff in song. Weather conditions seemed favourable for viewing Chiffchaffs, being relatively warm, with long sunny periods, but it was quite breezy. I soon heard my first singing Chiffchaff and spent the first hour or so locating singing birds and searching for colour ringed individuals. During this period I only observed collybita/western abietinus type birds, including two with colour rings (left leg - blue over blue and left leg - blue over green, both with orange/BTO rings on the right leg). Another collybita with colours blue over yellow on left leg and orange/BTO on right leg was also observed late morning.
At approximately 9.30am I finally heard a tristis type song coming from a hedgerow running north away from the sewage works. I quickly located this bird from the Kempsey Ham side of the hedge and observed it to be one of the pale individuals. I soon realised I needed to be on the other side of the hedge to obtain the best possible views of this bird and once this was achieved, superb views were had in good sunlight. This bird was observed for approximately one hour catching insects, as it moved through low Bramble and tall weed stems and was often noted flycatching from a wire fence alongside the hedge. Singing was heard on numerous occasions and the classic mournful peet call also heard at least five times.
This bird is considered the better candidate of the two pale individuals for being true tristis by other observers and myself and will be referred to as bird (A). The underparts were buff, particularly on the side of the breast and flanks, with the belly appearing more off-white. The supercilium was also buff and the ear-coverts a contrasting rusty/buff. No yellow could be detected on the face or underparts, but this can in some cases be impossible to confirm in the field. The crown, nape and majority of the mantle appeared uniform brownish/grey, with no obvious olive hue, but again olive may be present if viewed in the hand. An olive hue was noted on the closed wings, scapulars, upper tail, rump, back and possibly a limited amount on the lower mantle. The bill was small and dark, plus the legs and at least the top of the feet dark throughout.
The second pale bird (bird B) showed alongside bird (A) very briefly and its general appearance was very similar, with the exception of being a little plainer on the upper and underparts, but I couldn’t be sure regarding the presents of yellow on the underparts. The feet on bird (B) also appeared paler than on (A). The song of bird (A) expressed no similarities to western Chiffchaff, being a soft, rising and falling sequence of notes, at times slightly reminiscent of Willow Warbler in structure. It was also interesting to note that the bill was only slightly opened when the song was delivered.
By mid morning, bird (A) had moved to the hedge bordering the northern parameter of the sewage works. Looking up, with the sun behind the bird, its appearance seem a little different from the earlier views obtained. In particular I found it difficult to ascertain the extent of olive to the upper-parts, but I was still unable to detect any yellow on the face or underparts. By this point Brian Stretch had joined me in the hope of hearing the tristis song, but silence prevailed for the next hour or so. Eventually we did hear a bird sing predominately like tristis, but on two occasions, within a single song sequence, mix a single phrase of common Chiffchaff, ‘Chiff Chaff’, suggesting the song of an intergrade, but unfortunately this bird was hidden from view. This may have been bird (B), but we never managed to watch this bird sing or call so could not be certain of this. This mixed song was only heard once and thereafter only classic tristis song was heard.
It has been interesting to observe the change in appearance of these two paler birds over time. Both appeared whiter below, paler on the upper-parts, with olive restricted to the remiges when they first arrived at Kempsey in December. As the winter progressed both have developed more buffish underparts, become a darker brown on the crown, nape and mantle and an obvious olive hue was now present on the scapulars, back, rump and possibly the lower mantle. This must be due to the mid winter body moult.
To conclude, I can see no reason based on field observations and vocalization why bird (A) should not be a true tristis/fulvescens, but I still have not reached a firm conclusion on bird (B).
It is hoped another ringing session will take place here this weekend coming, weather permitting and that both birds may be trapped. If trapped feather samples will be taken for analysis. The ringing group is still waiting for the results from the third eastern type Chiffchaff ringed here in late December.
Andy Warr, February 28th 2007
The eastern-race Chiffchaffs at Kempsey
As in past winters, a small number of Chiffchaff (Phylloscopus collybita) arrived at Kempsey sewage works, to take advantage of the wealth of insect life attracted to the filtration pans and consequently the surrounding trees and hedgerows. Three individuals appear to show characteristics suggesting them to be birds of eastern origin, i.e. birds that breed east of the Pechora basin and the Urals. These birds are assigned to the race tristis and commonly referred to as Siberian Chiffchaff. Birds on the western side of this range are referred to as ‘fulvescens’ and were once believed to be an intergrade population between true tristis and eastern abietinus.
‘fulvescens’ is distinguished from true tristis by the presence of slight yellow streaking on the eye-ring, the supercilium and the underparts, and sometimes a little more olive on the upperparts. It is not paler than tristis. Intergrades between tristis and abietinus can provide considerable problems and only birds which match the full suite of characters (plumage and vocal) should be identified as tristis.
Also note that the yellow tones may be impossible to detect in the field. The most current thinking is that ‘fulvescens’ is now probably best regarded as a western form of tristis.
Two of the three eastern types are very similar in appearance and I have described them below:
Uniformed sandy brown upperparts, including the crown, scapulars and upper tail. Whitish underparts, with buff coloured flanks and side of the breast. The wings also appeared sandy brown and showed a slight green fringing to the edge of the primaries and secondaries, being paler on the latter, forming a slight wing panel. The ear coverts and the side of the throat showed a slight rusty/buff tinge, a little more obvious on one of the birds and the supercilium appeared buff. No traces of green on the upperparts or yellow on the face or underparts could be detected on either bird, but to confirm this, they would need to be examined in the hand. One bird showing pale tipping to the outer greater covert, forming a short wing bar and the second had a very narrow buff greater covert bar. Both had a small dark bill, with a pale cutting edge and dark legs.
Hopefully both these birds will be trapped in the near future and the race confirmed. I heard one of these birds, not sure which, give the classic Siberian Chiffchaff ‘peet’ call. Apparently both tristis and ‘fulvescens’ call alike.
The third eastern type was trapped, ringed and photographed on the 23rd December and was originally believed to be one of the birds mentioned above, but subsequent sighting of it in the field, revealed this bird to have darker upperparts and far more extensive buff underparts.
In the hand it showed the following features:
Supercilium, eye-ring, side of throat, side of neck, upper breast, under-tail coverts and flanks buff, plus further buff streaking on the lower breast and belly. Lemon yellow restricted to the axillaries and bend of the underwing. Ear coverts a uniform rusty/buff. Upperparts brown/buff, with olive flecking on the lower mantle, back, rump and scapulars. Upper mantle, nape and crown uniformed brown/buff. Olive fringing to the edges of the primaries, secondaries, tertials and tail feathers. Small dark bill, with pale areas to the cutting edge and a little at the base of the lower mandible. Legs black.
Adult eastern-race Chiffchaff trapped and colour ringed at Kempsey on 23rd December 2006.
Colours are dark blue over pink on left leg, BTO ring and orange on right leg.
The photo above shows clearly the contrast between the buff facial features and underparts, compared to the restricted lemon yellow on the underwing. This feature alone rules out ‘fulvescens’ as yellow would be present on the underparts and probably also the upper eye-ring and supercilium. The upperparts do appear more olive than would be ideal for tristis, but apparently a little on the lower mantle is acceptable and the presence of olive on the scapulars, back and rump is normal for tristis. The bill, though small as would be expected on tristis, does display a pale base, but this may possibly be acceptable on their western range. I have only heard this bird call once and it gave the classic tristis ‘peet’ note. When trapped, feather samples were taken and will be sent to be analysed. The results should tell us from where the bird originated.
After consulting with Alan Dean, co-author of ‘Siberian Chiffchaff’ revisited, British Birds August 2005, it was suspected that this individual, at best, came from the extreme west of the distribution of tristis, though beyond the area occupied by ‘fulvescens’, as the bird appeared rather olive on the upperparts but devoid of yellow away from the underwing. After a more critical examination of various photographs, Alan was of the opinion that there was slight, if very limited, yellow streaking on parts of the underparts and that, in conjunction with the rather olive upperparts, this suggested an intergrade.
The two paler, whiter bellied birds I suspect may fall into the ‘fulvescens’ category, or eastern abietinus/intergrade, but until trapped this remains to be seen.
Andy Warr, December 2006
The Willow Tit at Grimley
In early November a feeding station was established by Roger Blackmore at Grimley old workings. With feeders positioned in front of the Island Pool Hide many Blue Tits and Great Tits soon took advantage of this new food source. On 17 November Terry Norledge noted that a Willow Tit was making regular visits to the feeders and it also became apparent that the bird wore a metal ring on it’s right leg. Over the following few days with patient observation it was possible to read some of the ring numbers and together with some excellent photographs taken by Oliver Wadsworth and correspondence with John Hodson the ring number was finally pieced together. It transpired that this individual was one of two Willow Tits that had been rung as juveniles at Grimley old workings on 20 July of this year. A single Willow Tit was also noted here in mid-August but was not seen well enough to notice any rings. There were no further signs until the ringed bird was noted on 17 November.
 
These close up images helped to piece together the ring number. This individual is the first Willow Tit ever to have a ring read in the field. The ring number is T079872
Willow Tits had formerly been an annual visitor to Grimley, particularly during the autumn but with no records since 2003 the series of records this year are all the more significant in that a pair may have bred in the area. Willow Tit is in decline nationally and in Worcestershire the species now appears almost absent south of Worcester. The species is still hanging on in the north of the county with Bittell Reservoirs, Clent Hills and the Wyre Forest being the most likely sites at which to encounter a bird.
With thanks to Oliver Wadsworth, Mark Grantham at the British Trust for Ornithology and John Hodson, secretary of the Wychavon Ringing Group.
Brian Stretch, December 2006 |
