Barn Swallow parents sometimes get help from other birds to feed their young. These "helpers at the nest" are usually older siblings from previous clutches, but unrelated juveniles may help as well.
Amazing to us living in North America, a
large continent, is the extensive information
the small island of Great Britain has about its
birds. We use rough estimates, but in Britain
they have much more detailed information,
and so the population of each bird species is
known. Ornithologists (scientists who study
birds) in Britain also know how many breeding
pairs there are in Britain, their breeding success,
when and where they nest, where they
spend their time outside of the breeding season,
and whether the population is growing
or falling. To collect this information they use
several techniques.
Ringing birds is one technique. It is almost
100 years since the ringing of birds started.
These days a small, light-weight aluminum
ring coded with a unique number (and often a
contact address and color) is used, but some of
the earliest experiments with identifying birds
used thin silver wire or thread. Tracking birds
using rings is invaluable in establishing migration
dates and locations. People who may find
a dead bird can retrieve the ring and contact
the ringer with information. In the case of migrants,
this may occur in another country on
another continent.
While ringing provides certain types of information,
particularly the routes birds take in
moving around, and also where birds spend
their breeding season and off season, it does
not help with census information. This must
be collected using other methods. It is done
through an army of volunteers, who count
bird's nests, monitor their eggs and babies, and
generally watch their activities. This is done
using statistical sampling methods, allowing
the researchers to project based on the sample,
what is going on for the total population.
The volunteers are members of the British
Trust for Ornithology (known as the BTO), a
non-profit group formed in 1933 to conduct research
on birds. In many countries this work is
done by state and federal governments, but not
in Britain, where volunteerism is extensive, as
it also is in Texas and in United States. Volunteers
are assigned areas and bird species to
count and observe. The results are collected
and tabulated, then interpreted using statistical
analysis.
BTO published a magazine on its work and
outlining the results of its work. It is a most
interesting publication with stories about birds
lives. One story that piqued my interest recently
was written about Barn Swallows and
their breeding success related to the peaks of
insects that they collect for raising their young
(most baby birds need a diet high in protein,
and insects meet this need). As the insect population
peaks vary from year to year, so does the
breeding season of the swallows. What is not
clear to me is how the swallows know when
the insect population will peak. Presumably the
weather conditions needed by the insects also
stimulate the swallows to nest.
American Bird Conservancy, Cornell Lab of
Ornithology, and many local birding groups do
some similar work to the BTO, but we have a
long way to go to approach the great national
bird census data available in Great Britain.
Professor Tim Brush, PhD, ornithologist at
University of Texas RGV, is involved in doing
and directing bird breeding studies in our
area on tropical song birds. Harlingen author
Bill Clark, an expert internationally on raptors,
leads breeding studies on raptors in the Valley.
Mark Conway is a Valley bird bander, and he
regularly bands birds at Santa Ana National
Wildlife Refuge and elsewhere.
If you are interested in getting involved with
counting or banding birds in the Valley, contact
the author.
Christmas Bird Counts (CBCs) started in
United States and Texas in 1900. They occur
annually in the month either side of Christmas.
Typically about ten counts occur in and close to
the Valley. CBCs are useful, but are not statistically
based, so the information they produce
is useful only for estimating populations and
trends. Of more interest is e-bird, a program
of Cornell Lab of Ornithology, where every
day counts by birders may be entered into this
global data base. It collects data every day on
detailed observations and aggregates it. This
data is in the public domain and so allows for
analysis by a large number of observers at any
time.
We are surrounded by birds, but we don't
know very much about them, so we keep
guessing their status. As counting techniques,
the number of volunteers counting, and the
basis of counting improves, hopefully the day
will come when we know as much about our
Valley birds as they know about their birds in
Great Britain.