GREEN SCENE: Colony Farm is for the birds
Colony Farm Regional Park is gaining a reputation for being the birding hotspot in the Tri-Cities area.
With a diverse mix of habitats, including some regionally rare tall-grass meadows, the park attracts a variety of birds, including quite a few that are more reliably found in drier habitat of the Interior. The number of bird species found at Colony Farm is now over 200, so approximately 40% of all the birds ever seen in B.C. can be found at certain times of the year there.
This time of year, during the busy nesting season, is one of the more spectacular times for bird watching. The park fills with several species of warblers, flycatchers, vireos and sparrows, many of which have migrated long distances to reach Colony Farm.
The bird population in the park swells this time of year because so many birds fly from their southern winter homes to nest and raise their young here.
Why some species of birds undertake such long and remarkable migrations twice each year remains one of nature’s mysteries. Biologists believe these arduous journeys are worthwhile for the birds because the northern hemisphere produces an abundance of insects to eat as well as bountiful crops of berries and nuts during the brief summer growing season. These prolific sources of food plus the long daylight hours for foraging are thought to create ideal conditions for rearing the next generation. In contrast, in the tropics, summer daylight hours are shorter and competition can be fierce for scarcer food resources.
Not all the birds that arrive at Colony Farm each spring will stay to raise their young. Some of them simply stop to feed and rest, then continue further north. These include beautiful birds such as the ethereal mountain bluebirds, which will continue on their migration after a few days of feeding. Other birds, such as the western tanager, with its brilliant red head, will stop temporarily at Colony Farm and then seek out secluded nearby forests such as Burke Mountain to nest. Migratory birds require safe stopovers to rest and refuel during long migrations.
With the help of miniature radio transmitters coupled with clever experiments and many hours of careful observations, scientists are unraveling some of the mysteries of bird migration. Most songbirds are now known to migrate during the night. At dusk, these birds use the polarized light of the setting sun to take a heading for the each night’s flight. During the day, the birds rest and feed to gain strength for the next night’s journey.
Birds may also use the rotational patterns of stars to orient themselves in a north/south direction. While some of our birds, such as the colourful lazuli buntings and black-headed grosbeaks, migrate directly north from places such as western Mexico, others such as barn swallows, Swainson’s thrushes and purple martins fly from South America across the Gulf of Mexico and then head west to the Pacific coast.
Not only does each species of birds have particular migration patterns but individual birds appear to know exactly where they are going. This only makes sense — after all, if they have nested successfully in a certain location the previous year, then why not return to the same site? Nonetheless, such habits speak volumes for their amazing homing abilities.
Recent experiments have shed more light on the impressive homing skills of migratory birds. Biologists in Germany housed migratory European robins in sites screened from local background radiation and found these birds were able to orientate themselves to the magnetic field of the Earth. This suggested these birds also have a magnetic compass to use as a fallback when cloudy weather or fog obscures the setting sun and stars.
The most surprising finding was that, when these birds were exposed to very low intensity electromagnetic noise similar to what is used for AM radio transmission, they were no longer able to orientate themselves with the Earth’s magnetic field. This finding that very low intensity radio transmissions can interfere with the homing ability of birds suggests they are highly sensitive to such frequencies; this could also explain why migratory birds are sometimes fatally attracted to radio transmission towers. Previously, this was thought to be due to the lights that illuminate these towers at night.
Establishing parks to provide habitat for migratory birds, keeping cats indoors and drinking “bird-friendly” (i.e., shade-grown, organic) coffee are some of the things that people can do to help ensure migratory birds will have successful journeys and productive nesting seasons.
Elaine Golds is a Port Moody environmentalist who is conservation/education chair of the Burke Mountain Naturalists, chair of the Colony Farm Park Association and a founding director of the board of the Port Moody Ecological Society.