Anyone know what these hair-like nape feathers are? (1 Viewer)

I take a head shot of every weaver I catch and when going through them I keep noticing these long hair-like feathers on the nape. They are more noticable on the males, because they are black against a yellow background, but the females also have them. I was checking some today and they are not all over the body, just the nape. Does anyone know what these feathers are, and are they found in other species?

Tom

Hi Tom, these are filoplumes. See description below. They certainly seem to be more prevalent in tropical African birds than north temperate birds from my experience. Not sure why.

Filoplumes:
The simplest feather is the filoplume. It consists primarily of the rachis with no barbs or only a few isolated barbs at the tip. These relatively stiff and hair-like feathers lack specific feather muscles but have sensory receptors next to the base of the feathers. Filoplumes lie under the contour feathers and are thought to provide the bird with feedback on contour feather activity.
From: http://www.birds.cornell.edu/AllAboutBirds/studying/feathers/feathers

Thanks Ross. Your information helped me to look into it in a bit more detail. It seems that these filoplumes have a largely sensory function, as they lie beside other feathers so give feedback on feather movements. They connect directly to the cerebellum and are thought to have an important role in coordinating movements, such as during flight. The projecting filoplumes (which project above the contour feathers) seen on my birds, and present in many other passerine species, have been little studied, but I came across this paper on the possible function. They found that they are mainly on the nape and crown, in places where the bird cannot see or preen. They also tend to be more common on bird species with more flexible feathers or with a lower density of feathers on the nape. They looked at several possible functions and concluded that they were most likely there to enable the bird to know if the feathers in these regions are out of place, which could lead to heat loss. However, this is less likely to be a factor on a species that lives in Sudan, where heat loss is hardly going to be an issue. There is probably more that still needs to be studied here.

Tom

Filoplumes on the nape seem very common on passerines in the Neotropics, but I've never kept a list of which species I've seen them on, which might have been a good idea! I would imagine that many early type descriptions would fail to notice these feathers - it's only with the advent of high quaility digitial photographic equipment that I've noticed how frequent such filoplumes are.

cheers, alan

Filoplumes

lewis20126 said:

Filoplumes on the nape seem very common on passerines in the Neotropics, but I've never kept a list of which species I've seen them on, which might have been a good idea! I would imagine that many early type descriptions would fail to notice these feathers - it's only with the advent of high quaility digitial photographic equipment that I've noticed how frequent such filoplumes are.

cheers, alan

Click to expand...

I've noticed these on a number of species, including Chaffinches on which they are easily seen on high quality photos. My guess is that they perform the same function as 'air data probes' on modern fighter jets. That is they inform the bird's brain about the airflow over the body and allow angles of attack and sideslip to be sensed, this data is vital to allow the bird to adjust and control its flight.