Black-throated Green, Townsend's, and Hermit Warblers in Mexico
January 1, 2001 by Gregory Gough
Three closely related species of warbler: black-throated green, Townsend's, and hermit, have largely separate ranges during the breeding season in North America, but winter together in the tropics.
Scientists studied the birds on their wintering grounds in southeastern Mexico and found that they distributed themselves both by elevation and type of tree they foraged in.
The black-throated green warbler was found at low elevations, the hermit warbler in mid elevations, and the Townsend's warbler at the highest elevations. The hermit warbler ranged across the greatest elevation range and was often found in flocks with the other species. Black-throated green and Townsend's warblers were rarely found together.
The hermit warbler avoided competition with the other species by foraging primarily in pine trees, whereas Townsend's preferred oaks and the black-throated green foraged without regard to the type of tree. Black-throated greens foraged more often at the tops of trees and at the tips of branches and were more active feeders.
So, how did this distribution come to be? It is thought that the black-throated green warblers were the first to evolve of the three and occupied the most productive winter habitat. During a period of time between ice ages, they colonized the northern Rocky Mountains, evolved into the Townsend's warbler, and occupied the next most productive winter habitat, upslope from the black-throated greens. The hermit was the last to evolve, from the Townsend's, and occupied the least productive habitat, the pine trees in between the Townsend's and black-throated green.
This article summarizes the information in this scientific paper:
Greenberg, Russell S. and Gonzales, C. E. 2001. Non-breeding ecology differences between species in the Black-throated Green Warbler complex. The Condor, 103: 31-37.
- Transoceanic Migration by a 12 Gram Songbird
- Full-annual-cycle Population Models for Migratory Birds
- Migratory Songbirds Pick Breeding Site Based on Springtime Resources
- Bill Size Correlates with Telomere Length in Male American Redstarts
- Annual variation in long-distance dispersal driven by breeding and non-breeding season climatic conditions in a migratory bird
- Experimental reduction of winter food decreases body condition and delays migration in a long-distance migratory bird
- Incorporating site and year-specific deuterium ratios (δ2H) from precipitation into geographic assignments of a migratory bird
- Inter-annual variation in American redstart (Setophaga ruticilla) plumage colour is associated with rainfall and temperature during moult: an 11-year study
- Characterizing Avian Survival along a Rural-to-Urban Land Use Gradient
- Modeling Three-Dimensional Space Use