|The Orange-crowned Warbler (Vermivora celata) breeds widely over western and northern North America, and east across Canada. There are four recognized subspecies of this warbler. One of them, the sordida subspecies (Vermivora celata ssp. sordida), is endemic to the Channel Islands and reaches its highest density on Santa Catalina Island. This subspecies is fairly different from others that breed on the continent, however, its life history is poorly known.|
While mainland Orange-crowned Warblers are long distance migrants and strict ground nesters, the sordidas are year round residents on the islands or migrate a very short distance to the coast of Southern California and nest in shrubs or trees as well as on the ground.
In March 2003, researchers from the Smithsonian Migratory Bird Center and the University of California at Riverside began a long-term study on Santa Catalina Island to better understand the life history and ecology of this warbler. One hundred individuals including males, females and nestlings were captured and banded. This banded population will allow determination of which proportion of the population stays year round or leaves the island during the fall.
Over 90 nests are being monitored. On the island, these warblers start breeding in early March and nest mainly in shrubs (Lemonade berry, Coyote brush, Monkey flower), although several nests were found on the ground as well as in trees (Island scrub oak) at 3 or 4 meters high. A very interesting finding is that the island sordida warblers are double brooders, in contrast with the mainland Orange-crowned Warblers that have only one brood a year. Orange-crowned Warblers feed by gleaning insects from plant leaves. During March the warblers forage mainly on oaks and in late April and May they also get many insects from the grass and nectar from flowers.
We are approaching the end of the breeding season for the sordida Orange-crowned Warblers and the field is loaded with newborn fledglings. So, hurry up, get your binoculars and try to find them! If you are lucky you will get to see their puffed orange crown.
Note: If you encounter any banded bird try to get the color combination on its legs and please let us know when and where you saw it.
You can email the researchers Susana Peluc