| Patuxent Science Meeting 2006 Poster Abstract |
| | Behavior and Ecology of the Alder Flycatcher (Empidonax alnorum) in |
| | early winter |
| | Foster MS |
| | Before the status and vulnerability of a species can be accurately assessed and an effective |
| | management plan for its protection developed, year-round threats to its well being must be |
| | considered. Yet information about the biology of Nearctic migrant birds during migration and on |
| | their wintering grounds is scarce. The Alder Flycatcher (Empidonax alnorum) is one of the |
| | species for which migratory and winter behavior and ecology are especially poorly known. |
| | These birds winter on the eastern slopes of the Andes and into the adjacent lowlands from |
| | central Colombia south into northwestern Argentina. They occupy shrubby clearings, open |
| | woodlands, and dense brush, especially adjacent to water, as well as primary-succession |
| | habitats along the shores of floodplain rivers. I studied the early winter ecology and behavior of |
| | Alder Flycatcher along a white-water meander river in Manu National Park, Peru during October |
| | and November from 1993 to 1997. The birds occupied territories in the primary-succession |
| | habitats on growing point bars. They were most common in mixed stands of Tessaria integrifolia |
| | (Asteraceae) and Gynerium sagittatum (Gramineaceae) interspersed with bare sand areas. The |
| | uneven height of the Tessaria canopy, which resulted in openings in the vegetation large |
| | enough for the birds to flycatch, was an important habitat feature. Birds obtained insects |
| | primarily by aerial hawking (91%). Fruit formed four percent of the diet. Territories ranged from |
| | 0.04 to 0.25 ha and were occupied by one, two, or three birds. Every territory had one |
| | dominant individual who was primarily responsible for territory defense; the other birds were |
| | subordinate. Vocalizations given included the fee-bee-o song, a two-syllable song, and the pit |
| | note, which are also given on the breeding grounds. A series of pits given increasingly rapidly |
| | signaled a territorial interaction. In the least aggressive encounters, the birds remained on their |
| | territories and countersang or exchanged agitated calls. In boundary disputes the birds engaged |
| | in a vocal duel at a common territorial boundary. In the greatest intensity interactions |
| | dominants chased intruders out of the territory. Dominant birds, which sang the full song, likely |
| | were adult males. Immature males do not sing a full song, and females are not known to sing in |
| | nature. Subordinate individuals were likely females or young males. At present, Alder |
| | Flycatcher populations show no evidence of declines. However, the behaviorally dominant |
| | Willow Flycatcher appears to be expanding its breeding range northward, displacing the Alder, |
| | whose breeding range is shrinking. Loss or degradation of riparian habitats could also become a |
| | factor on both the breeding and wintering grounds. The floodplain habitats along meander rivers |
| | in the Amazon Basin, which are renewed each year by depositions of silt, are highly fertile and |
| | suitable for agriculture. In addition, plant species (particularly Tessaria) characteristic of the |
| | primary succession are especially fast growing and produce fiber suitable for paper pulp. |
| | Because these primary succession habitats are constantly being renewed, however, it may be |
| | possible to develop land-use plans in which only the post-Tessaria successional stages are |
| | Friday, September 22, 2006 |