rib cage. Feathers can be bent to some extent, but shafts of remiges and rectrices
should not be broken, as this will affect flight. Remember that many heavy-billed
herbivores can inflict a nasty bite, as can most piscivores, and that raptors strike
with the feet as well as the bill. Especially in the tropics, liquid iodine is considered
vital for scratches and cuts inflicted by birds.
4.6 The bird at close quarters
Once the bird has been identified and ringed, various other attributes can be
recorded, and samples taken, before release. The measurements listed below are
described in greater detail in Pyle et al. (1987), Baker (1993), Jenni and Winkler
(1994), Svensson (1994), and Redfern and Clark (2001).
4.6.1Age and molt
Birds are aged in years relative to the year of hatch, and apart from nestlings and
nidifugous precocial young, whose hatch-year is obvious, age is best determined
from plumage and soft-part details. Guides to ageing are available for European
and North American birds, but knowledge of the molt pattern of the species is
also useful. In strongly seasonal temperate latitudes, this poses relatively little
problem since most species breed at a specific time of year and the molts fit into
a well-defined cycle (breed–molt–{migrate}–{molt}–{migrate}–breedetc.), and
in Europe and North America excellent handbooks containing such details are
available (e.g. Pyle et al. 1987; Baker 1993; Jenni and Winkler 1994; Svensson
1994). But in areas where the timing of breeding is less well defined, for example
“during the rains,” these cycles may be less clear and, coupled with or general
ignorance of the species concerned, this means that ageing the birds can be diffi-
cult or impossible. In these situations, it becomes important routinely to record
soft-part details such as the color of iris, bill, mouth-lining, feet, and bare facial
skin routinely since these may enable you to age the birds retrospectively when
you have worked out how. For example, some nestling passerines (e.g. Sylvine
warblers [Svensson 1994], and Indigobirds [Payne 2002]) have tongue-spots,
which remain until after fledging, and these can aid ageing.
Here also, skull ossification may be valuable. In passerines the cranium is not fully
ossified at fledging. This means that there is effectively a “window” in the bone
which is visible beneath the skin (without surgery). However, “skulling” must be
performed with the feathers parted in very good direct light and is difficult to learn
without guidance. Also, the rate of ossification differs between species so that, while
a bird with incomplete ossification of the cranium is undoubtedly juvenile, one with
an ossified cranium is not necessarily adult; it depends on the month of observation.
100 |Birds in the hand