Tillamook Coast Life Blog
Visitors from Mexico: Tropical Kingbirds
On October 25 another birder found one along Sand Lake Road, a quarter mile south of the Sand Lake Grocery.
These are conspicuous birds near the size of a Robin, with bright yellow underparts, gray backs and heads, and big black bills. They commonly sit in the open on elevated perches, particularly treetops, fences, and overhead wires. Tropical Kingbirds breed from southeastern Arizona south through Mexico and Central America and over much of South America. This is, however, also a species that occurs annually in small numbers on the California and Oregon coast, and some years even into Washington and British Columbia.
Best localities for seeing Tropical Kingbirds in Oregon are in fairly open country near the coast with some elevated perches. Common habitats on the Oregon coast include residential areas with lots of trees, former pastures grown up to blackberries and saplings, and the hedgerows and groves of trees in dairy country.
Kingbirds are large flycatchers – birds that fly out from perches to capture flying insects. Nearly all the flycatchers that breed in Oregon migrate south for the winter, to places with better winter food supplies. So what are Tropical Kingbirds doing migrating north, when their relatives are clearing out? This is a bit of a mystery, but it tells us some interesting things about bird navigation and migration.
Birds that are found far out of their “normal” range are called “vagrants,” a term that for birds relates more to their straying than to any lack of “visible means of support.” By definition vagrancy is rare, for if occurrences were more common we would think of them as normal occurrences rather than straying. However, for many species, including Tropical Kingbirds, vagrancy has occurred often enough that patterns can be seen that shed light on its occurrence.
Tropical Kingbirds are quite common in much of their huge range, so that quite a few can stray, and still be rare, relative to the overall population. The ones breeding closest to us are in northwestern Mexico and barely into southeastern Arizona. These northern birds are migratory and each fall fly south-southeast at least into southern Mexico and perhaps as far as Central America.
In many birds, including several other species of flycatchers, much of the recorded vagrancy involves “reverse migration” which means flying the opposite direction from what is normal. Thus a few Tropical Kingbirds which normally migrate south-southeast out of Sonora and Sinaloa, instead fly north northwest, ending up on our Pacific coast. They have an innate code that controls fall migration, specifying timing (usually October), direction (south southeast), and probably distance. They also have to have a means of determining direction, i.e. some sort of internal compass. So the ones that visit us have a flaw, either in the direction code or perhaps more likely, in the compass. In effect they are mistaking the black needle of a compass for the red one. These vagrants are likely immatures, although in this species immatures are difficult to distinguish from adults in the wild.
So what happens to these southern visitors? They move up the coast, and some find locations where they can stay for a while. Most disappear when the weather gets cold, but some set up residence, and try to overwinter. A very few seem to succeed, if they find a good enough place, and have a mild winter. They need to get food pretty much every day, so a place with lot of insects is important. Dairy farms with manure storage facilities tend to have insects even on cold days, so they might provide particularly good spots. Areas around shallow ponds and sloughs may also have decent winter insect supplies. In cold weather these birds may also eat small fruits, such as the berries of Mountain Ash, Holly, or Hawthorn trees. Again, farm country may give them the best chances. Alternatively, a residential section of town might also work, if it has lots of ornamental trees with fruits that persist through the winter, and backyard gardens where last summer’s plants are left to self-compost.