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Tracking Birds
by Keith Hackland
published September 2017



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.