When a bird is your habitat, you have to fit in and hold on.
Sometimes it seems like birds get all the barracking in the carnival of life, but they get more than their fair share of mites too. In fact, birds provide mites with a host of microhabitats into which they inveigle themselves. Some of these you might expect, such as nostrils, lungs, air sacs, around the cloaca, in the skin, or under the scales of the feet. Others take some imagination, such as the several radiations of quill mites that enter the small opening of the umbilicus of a developing feather and spend their lives – usually several generations worth – inside the feather quill. Most of the mites living on birds, however, are not so nasty and may be useful – the vane-dwelling feather mites – which seem to glean their living from the debris and oils that accumulate on feathers.
As one might expect, vane-dwelling mites live on the surface of the flat flight feathers of birds – mostly in the narrow lanes formed by the barbules, the parallel channels that run out from barbs that run out from the rachis. These feather mites seem to fit their barbule widths to a T, especially on the wing feathers, where aerodynamic forces are uncompromising. Actually, feather lice have been shown to fit their spaces, but except for those mites that live on birds that dive or swim under water, it is just an assumption for feather mites. However, finding and holding on to a potential mate in these circumstances is clearly a challenge as these complexed mites from the feathers of a Pale-headed Rosella (Platycercus adscitus) show. You can see the expanded posterior of the male (with suckers underneath for holding on) and the energetic grip of legs IV on the larger female, but what happens next is a bit of a mystery.
