Saturday, 27 January 2018

Frogmouth Fledglings

two weeks and two months out of their nests

This pair of frogmouth fledglings have been out of their nest for two weeks, so as they were in the nest for four weeks, they are now six weeks old.

It is now January and most of the young frogmouths have left their nests, all those in my study areas have. When they do so, they become more obvious to people out walking and I am frequently asked how I can tell the age of the fledglings. So, here is a brief guide to the telling young and old frogmouths apart, using birds of known age.

This is the same pair seen in their family group. Mum is up top and dad is next to the chicks on the far right. He is slightly larger than the adult female and she has red on her wing coverts. Although the fledglings are well feathered, they are still only about half the adult size and weight.

The chick on the left is probably a male because it has grey coverts on its wings, the other one, in the middle, is probably a female as it has red/pink colouring on its coverts. Both can fly quite easily between trees as their wing and tail feathers are well developed, although their tails are not fully grown. Both chicks still have much fluffy down feathers around their heads and bellies, this is probably the best indicator that they are still young birds. The adults' body feathers lie smoothly against their bodies, except one stray feather on the male's upper wing which it is in the process of moulting out.

In a neighbouring territory, the fledglings have now been out of their nest for two months (so they are three months old) and they look much more like adult birds. In the above photo, the bird in the fore is a fledgling, that behind is its father. The bulges of stray downy feathers on the young bird's flanks catch the light as they stick up from the body. Those on the adult male lie flat and the under-tail coverts are longer and well streaked.

As most people view frogmouths from below, it is perhaps best to focus on what can be seen from below to guide aging these birds. And tails are the most obvious feature from that angle. The adult's tail on the left is long and smoothly edged. The youngster's tail on the right is shorter and ragged. The individual feathers are smooth, but they are of different lengths as they grow. When scrutinised, the young birds tail feathers look very smooth-tipped, the adult's tail fathers are usually frayed and chipped with wear as the bird has had most of them for a year or more. They will have pairs of fresher feathers within the mix as new ones are grown in replacement of those moulted out, but it is difficult to see that detail in the field.

In another month, they will be almost indistinguishable, but there are ways to tell.

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