| Audubon's Oriole (Icterus graduacauda) was known historically throughout the Lower Rio Grande Valley (LRGV) of Texas, but its breeding range has now declined to mainly riparian habitat in Starr County. Habitat loss, degradation, and fragmentation, and brood parasitism by Bronzed Cowbirds ( Molothrus aeneus) are likely causes of this decline. Habitat patches where Audubon's Orioles were present were larger, with a larger vertical range of canopy, greater vegetation volume, greater richness of bird and woody plant species, less local deforestation, and less local habitat fragmentation than where Audubon's Orioles were absent. Bronzed Cowbirds showed no numeric correlation with Audubon's Orioles, but their presence was associated with smaller habitat patches. Bronzed Cowbirds responded to tape playback of Audubon's Oriole song, and their response was more frequent than expected at sites of Audubon's Oriole presence. If the trend of habitat degradation continues in the LRGV, Audubon's Orioles will have fewer places to breed and these places will be more susceptible to brood parasitism, likely resulting in a further decline of Audubon's Oriole in the LRGV. |
