Long-established firms have wide experience with many species, and some
have biologists to plan the optimal tag (and project) design for each biological
question. Therefore, choosing the right firm is in many ways more important
than choosing the details of the tag. Read web-sites carefully and ask other
researchers in the same field for advice. Many prefer, where practical, to stay
with proven tag types until new designs are well tested. Conscientious manu-
facturers provide details of their quality controls, such as temperature-cycling
systems.
Receivers for VHF projects last a long time, so it can be wise to obtain capabil-
ities beyond the immediate needs, if the budget permits. Tags are identified by sep-
arate frequencies, typically 10 kHz apart. A pilot project with low budget may have
to manage with a receiver for 10–20 tag frequencies. However, subsequent quantit-
ative work will need to distinguish many more tag frequencies. Most receivers cover
a band of only 1–2 MHz, but one new model covers most of the VHF band and is
therefore suitable for projects in many different countries. It is convenient to store
frequencies and, if you need to search for tags on dispersing or wide-ranging
animals from moving vehicles, to scan automatically through them at chosen time
intervals.
As an alternative to these specialized receivers, commercial “scanner” receivers
are available at low cost to cover the same frequency range. However, their scan-
ning is for seeking signals, not to dwell on pre-set frequencies. Moreover, these
receivers are not designed with gain controls suitable for close-range tracking, or
to be robust, waterproof, and easy to use with gloves. They are therefore best for
undemanding tracking and to keep in reserve for when the mainstay receiver
is unavailable. Servicing requirements of specialized receivers should be infre-
quent, but check when buying for availability of prompt servicing or loan in case
of emergencies.
Any receiver can be used for logging data. The simplest logging involves record-
ing the signal from a headphone socket onto audio or paper tapes. This approach
typically records for one tag frequency at a time, for instance to record presence on
a nest. Several tagged birds can be recorded visiting a feed site if the receiver will
step through frequencies, provided that one channel records an identifier signal.
Alternatively, a receiver may have an interface for data transfer and for control by
auxiliary hardware. Some tracking receivers that lack an interface in the basic
models can have it added as an option. Very sophisticated logging is possible with
such systems, for instance to check some frequencies more often than others
or even to provide paging or other alerts for rare events (e.g. probable death or
dispersal).
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