returned to its roost site as soon as possible in darkness. Roost sites should be
monitored subsequently (visual inspection during the day for droppings may be
sufficient) to assess the roost-desertion rates from this method, as a shortage of
suitable roost sites might affect the survival prospects of small birds in winter.
Other direct capture methods have been devised for a range of species. For
example, batfowling is a traditional method of catching seabirds on land by using
a long-handled hand net held above the head, and if approachable, swans can
be caught with a swan-hook: basically a pole with a metal hook like a narrow
shepherd’s crook.
4.4 Individual marking
Birds are marked whenever it is necessary to identify them either as individuals,
or as members of a class such as a particular cohort. In general, individual iden-
tification is to be preferred (see Chapter 5). Always fit any ring or mark before
taking any measurements, in case the bird escapes, but only after it has been
identified to species (or subspecies if relevant).
As implied above, the universal marking method for birds is the leg ring (ring or
band) fitted to the tarsometatarsus (below tarsal joint, not tibiotarsus above joint),
but it is not the only kind of mark available. Metal or plastic rings are available in
a variety of sizes (e.g. 27 in the United States and the United Kingdom) covering
everything from hummingbirds (United States), whose bands must be trimmed to
fit (see NABM), to swans. Metal rings carry a unique number and usually (depend-
ing on size) an address to which a finder can report the ring (e.g. Zool. Mus.
Denmark). They are also available in a variety of designs and metals (from pure
aluminum to stainless steel) depending on the biology of the birds concerned and
the risk to the ring of wear or corrosion. These rings are obtained in series or strings
of, for example, 100 rings numbered in sequence (e.g. VA32101–100).
For recovery, metal rings generally require recapture of the bird for the inscrip-
tion to be read. Plastic rings are generally for individual identification in the field
without recapture. For smaller species, they are typically available as plain (i.e. no
inscription) celluloid split rings in a variety of colors, which are applied singly or
in combination. These rings are manufactured commercially for the pet trade.
For larger species (not feasible if internal diameter less than 8.0 mm), rings can be
engraved and made to measure by the researcher from plastic laminate (DARVIC),
which hot water softens enough to shape in a simple mould.
Metal rings are fitted with specially designed pliers. In some schemes, the rings
have to be opened (e.g. with circlip pliers) before they can be closed on the bird’s leg
(Figure 4.1). Plastic color-rings are fitted with a tool like a shoehorn. Large
Individual marking| 95