Uninvited guests in the nest

Having recently described the unexpected discovery of an occupied song thrush nest and the subsequent successful fledging of the chicks, being a bug-nerd at heart, I felt the need to have a closer look at the nest itself once it was no longer in use to see if any small invertebrates lay within... However, this isn't just random nosiness - there are many parasites that live in the nests of birds and mammals, and it's also the type of place where overlooked species may be found - after all, not that many people are likely to check. So, white tray in hand I began to sift...

The first species to popout was a barklouse or psocid (Psocoptera). This group contains many small species that are associated with bark, dry plant material and so on. I won't go into too much detail here, but the specimen was about 1.5 - 2mm long, variably brown with yellow and brown markings on the head, and the wings held like a shallow roof over the abdomen. Helpfully (as these tiny creatures can be tricky), the forewings also had a pattern of spots that indicated the genus Ectopsocus. As it happens, this pattern is quite strongly diagnostic and as you can see below, the spots are at the end of the wing veins and extend along them so are about twice as long as wide. This provides an identification as E. petersi - an interesting find as it is probably under-recorded, having previously been placed in the 'E. briggsi' group of similar species. However, if any psocid specialists are aware of further taxonomic changes, please do let me know.

Forewing of Ectopsocus petersi

The second species was about the same size (1.5 - 2mm), but quite different in structure - as well as the prominent bristles, it also had a relatively large ventral spring joined to the rear of the abdomen - clearly a springtail (Collembola).The blue-grey colour, which I admit was clearer in the specimen than the photos below), and other features of the ocelli, bristles and spring, plus a dark spot between the antennal bases, suggest that it is Entomobrya lanuginosa (E. myrmecophilus is associated with ants, rare and with longer bristles, while Willowsia have leaf-shaped scales rather than the covering of bristles). This is usually coastal, but inland sites are known, and a bird nest seems perfectly reasonable for a species that can be found in dry, sheltered locations.

Entomobrya lanuginosa

Close-up of Entomobrya lanuginosa

So, an urge to investigate, and a bit of work, turned up a couple of unexpected species. Possibly not as immediately engaging as nestlings becoming fledgelings (though, my bug-nerdiness means I do like them pretty much equally), but as always, species records are valuable, especially for under-recorded taxa.

References

Hopkin, S.P. (2007). A Key to the Collembola (Springtails) of Britain and Ireland. FSC, Shrewsbury. The current standard work for UK species - excellent.
New, T.R. (2005). Psocids: Psocoptera (booklice and barklice) (2nd ed.). Handbooks for the Identification of British Insects 1(7): i-iv, 1-146. Also the current standard work for UK species - also excellent.