We got very lucky this morning after following yesterday's two probable Pallid Swifts (found by the Hunters) presumably one of the same birds did a fly by (picked up by Marc Read) allowing us to get some better photos which appear to confirm the identification. The bird could have done with being closer and in better light but I think we've got enough but will have to wait to see if the BBRC agree.
Presumed juvenile/first-winter Pallid Swift (above and below). The extensive and broad pale throat that extends below and beyond the eye and the pale forehead with an 'alien-eye' appearance all look good for Pallid. Structurally the bird also looks good for Pallid (see below) and the crown appears relatively flat (compared to the steep forehead of Common Swift). Furthermore there doesn't appear to be a strong contrast between the lores and the ear coverts. Typically juvenile Common Swift has a very contrasting and restricted white face with small white clearly demarcated throat patch and white lores that contrast with the ear coverts. Common Swift also often has a prominent white leading edge to the wing which is not apparant here either.
Structurally the bird appeared to have a relatively shallow tail fork and broad arm and a relatively stocky caudal projection (above and below). The wing-tips also appear relatively blunt tipped. The lack of moult and the apparant fresh and uniform feather tracts indicate a juvenile/first-winter bird.
In comparison Pallid Swift from today (above) and Common Swift (below)- Common Swift has a more rakish appearance, with a thinner hand and pinched in caudal projection and longer tail. Sadly there is only a hint of scaling on some images (more or an adult id feature anyway as both juvenile Common and Pallid can appear quite vermiculated on the underparts) and there is not enough detail in any of the photos that I got to see any finer details such as the contrast in the coverts and primaries or much in the way of overall colouration. However the pictures the Hunters got yesterday show milky brown coloured birds so hopefully by putting together all the details available- the large diffuse pale throat extending beyond the eye, the contrasting eye mask, the relatively broad bluntish tipped wings, the stocky caudal projection and the relatively shallow forked tail and the overall milky brown colouration captured in yesterday's images - seems on balance to favour Pallid Swift. In context of the time of year and the intense warm southerly airflow over the last few days that fits in with an established vagrancy pattern for this species- seems like a strong case for Pallid Swift.
Yesterday's birds showing the milky brown colouration (Liz Hunter)
Pallid Swift from Bulgaria above and Common Swift from Beddington below highlight some of the stuctural features as discussed above. These are both Spring birds but the structural features carry across as does the face pattern on these particular individuals.
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Weather chart for yesterday at around mid-day when the birds were first discovered. A deep southerly strong airflow originating from Iberia was in place. Pallid Swift are double brooded (unlike Common Swift) and late fledging birds on orientation flights getting carried north in strong tail winds are believed to be involved in these regular vagrant events to NW Europe in late October/November. Interestingly there was a Common Swift seen at Spurn today and in past late autumn 'Swift events', Common Swifts have also been involved so caution is required.
References/Sources used:
Common and Pallid Swifts Photo Identificaton, Birdwatch, Andy Stoddart HERE
ID Handbook of European Birds, Nils van Duivendijk
Advanced Bird ID Guide, The Western Palearctic, Nils van Duivendijk
Flight Identification of European Passerines and Select Landbirds, Tomasz Cofta
The Identiication of juvenile Common and Pallid Swifts, Hans Larsson, British Birds: 111: 310-322
