Spring Arrival of Summer Resident Birds on the Lower Rio Grande, New Mexico

Abstract

The spring arrival dates in the Mesilla Valley, New Mexico, for eighteen species of summer resident birds are presented graphically. The relatively orderly arrival of migrant birds to their breeding areas is a phenomenon fully appreciated but not documented for many specific areas in North America. This report is concerned with dates of arrival of summer resident birds in the Mesilla Valley, Dona Ana County, New Mexico. The Mesilla Valley is part of the old flood plain of the Rio Grande. General elevations lie at about 3900 to 4000 feet. Much of the native riparian vegetation has been removed to make room for intensive agri- cultural and urban use of the area. There has also been serious overuse of the existing water supplies so that additional ecological change has occurred in association with a lowered water table. Our data refer to a period in the history of the Mesilla Valley when these changes had not been fully effected; the picture we want to present will thus be more nearly representative of the one that existed prior to man's widespread use of the area. For this reason some birds, such as the Chat (Icteria virens), Yellow-billed Cuckoo (Coccyzus americanus), and the Painted Bunting (Passerina ciris), are treated here although they no longer occur sufficiently abundantly that ade- quate data can be recorded. Records we consider satisfactory exist from the period 1924 to 1940. In this time the senior author was in the employ of the United States Bureau of Reclamation and was in the field in a great variety of habitats practically all spring and early summer. His activities were such that a reasonably uniform type of observation was possible all during this time, except in 1927 and 1928. Thus, a maximum of 15 years of first dates are recorded for some species represented here, with a lesser number for the remainder.