Stranger in the basement

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Not many birds today, either, but two species I haven’t searched before on this trip:
Rock Pipit Anthus petrosus
Marsh Warbler Acrocephalus palustris

Neither of these had lice, and of the 28 birds searched today (plus one Chaffinch Fringilla coelebs searched last night), only a Red-backed Shrike Lanius collurio and a Ruff Philomachus pugnax had any lice. The great weather that was supposed result in a huge downfall of birds during the night didn’t result in any such thing, as far as I can see.

We did get a surprise visitor today, though. Christopher (the bander in charge here) found a European Viper Vipera berus in the basement. I don’t know how it managed to get in there, but it was trying to climb up the stairs. It got up the first step, but then there were people in the way, so it returned down and eventually we got it up on a shovel and carried it out into the wild again. Here are some pictures:

OLYMPUS DIGITAL CAMERA

OLYMPUS DIGITAL CAMERA

OLYMPUS DIGITAL CAMERA

Incidentally, I also passed 700 searched birds today. 1000 is not impossible. The most I’ve ever searched in one collection trip was 1008, in Japan, so this may be the time to break that record.

I’ve had some more thoughts about differences in lice of non-migratory/migratory birds, though. If there are actually more lice on birds in Southern Europe than up here (the first step would obviously need to be to verify this!), how should this be tested properly? But:

How do I know where the bird comes from?

Just catching birds indiscriminately in (say) Spain or Italy during migration wouldn’t work very well, as I wouldn’t be able to compare that with data from Sweden in any meaningful way. While I can be reasonably sure that birds caught here are Northern breeders (or descendants thereof in the case of first-year birds), the same cannot be said about birds caught in the Mediterranean, as those catches would obviously include birds from Northern Europe, and the comparison would be between {Strictly Northern European birds} and {A mixture between Northern and Southern Birds}.

One way to solve this would be to focus (in Southern Europe) exclusively (1) on southern subspecies of widely distributed birds. This would mean that I’d have data for the same host species (= very closely related genetically, at least) from different parts of the breeding range. The main problem with this method would be that most intra-European differences in subspecies are very subtle, mainly being based on measurements and hard-to-separate colour differences. Banders may not want to, have time to, or be able to separate these while banding, and it is likely that I wouldn’t be able learn to to tell them apart myself during a single banding season. The southern data set would therefore still likely be a mixture.

This could be avoided by catching birds at breeding grounds, during breeding season, in both Sweden and the Mediterranean. Then I would know that, regardless of the subspecific status of the birds, they would at least be separated in breeding grounds, and thus could be sorted into Southern and Northern breeders, with no regard to taxonomy (horrid thought!). This is feasible, but the main drawback may be that it may prove tricky to find birds that I could catch in both areas in large enough quantities to be able to say anything at all. I’m guessing that catching in nesting boxes or nests would be the easiest, and perhaps House Martin Delichon urbicum or some tit may be the most suitable candidate. Several species of tits breed both here and in Spain, for instance, so this might work.

It may also work to use sister-species that are distributed across Europe. Pied Flycatchers Ficedula hypoleuca and Collared Flycatchers F. albicollis could be two candidates here in Sweden, with Semi-collared Flycatcher F. semitorquata replacing/augmenting these in Southern Europe. Guillermo who was here recently was catching a lot of Sylvia warblers in Cordoba, and that could be another suitable candidate group, with several species that breed primarily in the North, such as Lesser White-Throat S. curruca, and several that breed exclusively in the South, such as Subalpine Warbler S. cantillans. This would be a weaker test, however, as there may be other effects that would produce a difference in infestation rates.

Shirihai et al. (2001) shows that there is a Mediterranean group of Sylvia warblers which is sister group to Common Whitethroat S. communis, and another Mediterranean/Arabian group that is sister to the S. curruca superspecies, while the Blackcap S. atricapilla and the Garden Warbler S. borin are sisters to all other Sylvia (Barred Warbler Sylvia nisoria, the desert warblers, and the old Parisoma warblers would be harder to get hold of large numbers of, I guess).

This suggests that, given that large amounts of at least a few Mediterranean species could be caught, we might be able to correct for phylogenetic effects somehow, as the Northern species are scattered inside the phylogeny.

Though possibly a combination would work best to establish whether or not lice actually have higher infestation rates in the Mediterranean. Catching both species that occur both in Sweden and in (say) Spain, and species that occur in either, but not both, would result in both comparisons between and within species, throughout the phylogeny of, e.g., Sylvia.

I think this is something that needs much more thought, but could potentially be worthwhile. Of course, if I find that the infestation rates on Mediterranean birds is as low as the ones here, that’s pretty much a dead end…

(1) Of course more northern individuals shouldn’t be neglected entirely, but the subspecies differences should be noted so that the data set can be divided afterwards.

Shirihai, H., Gargallo, G., Helbig, A.J. (2001). Sylvia Warblers – Identification, taxonomy and phylogeny of the genus Sylvia. Christopher Helm (Publishers), London. 576 pp.

One response »

  1. Update:
    We just caught two White Wagtails (no lice) and a Lapwing (some Menoponid on the wings). It is so much easier working with shorebirds…

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