Summer Tanager

Summer Tanager

San Pedro Riparian National Conservation Area (SPRNCA) is home to an incredible diversity of bird species. Sitting at the junction of the Rocky Mountains to the north, the Sierra Madre to the south, the Chihuahuan Desert to the east, and the Sonoran Desert to the west, there are 100 species of birds residing here.

Each year, these resident birds are joined by millions of migrating birds in 250 species during the spring and fall migrations. The San Pedro and Santa Cruz Rivers are vital corridors for north-south migration across the arid Southwest.

The Bureau of Land Management must take the needs of these species of animals into account when setting policy for the SPRNCA to ensure their current and future health. Good decision making requires careful study and the ongoing collection of accurate data. This is where MAPS comes in.

The basic MAPS process is to use fine mesh nets to capture birds during the summer nesting season. Station operators examine the birds for age, sex, body condition, and reproductive status. Captured birds are given a light-weight, numbered aluminum leg band and released unharmed. Subsequent recapture of banded birds provides valuable insight into survival, reproductive rates and movement patterns.

Since 1989 information has been collected at over 2,000 MAPS stations located throughout the U.S. and Canada. Capture stations are run by independent parties, state or Federal agencies, and by contractors working for the Institute for Bird Populations (IBP). Studies based on MAPS data have highlighted the importance of the survival of first year birds which is linked to wintering grounds and migration routes. This, in turn, points to the importance of weather, the timing and extent of precipitation, and its impact on habitat as a key factor in the survival of avian populations.

The key issues that MAPS is designed to examine are: What factors drive avian population declines? Where are problems most acute, on the breeding or non-breeding grounds? What drives differences in trends between particular regions or habitats? What is the relationship between population change and weather, climate, or habitat loss? What can we do to reverse declines in population?

MAPS data has recently been used to look at the impact of urbanization, the effects of climate change, survival rates of birds in different areas, and the use of riparian areas. Another MAPS initiative is to map migrations. Banding data coupled with genetic analysis of feathers allows the mapping of populations of migratory birds during their annual migration cycle.

An example of a project that makes heavy use of MAPS data was the Lower Colorado River Multi-Species Conservation Program. This Bureau of Reclamation project is seeking to restore wildlife habitat in the lower Colorado River area of Arizona and California, an area that was once a major migratory route and habitat. Data on bird species and their use of restored wetlands has been critical to efforts to recreate historic habitat. Species at the center of the study include the yellow warbler, Bell’s vireo, Gila woodpecker, and summer tanager.

A MAPS banding station operated by the BLM near the San Pedro House captures, examines, bands and releases birds unharmed. The information collected is vital to an understanding of what species use the riparian area along the San Pedro River at what times. The aggregate of data collected over a period of years provides a picture of the health of the population of resident and migratory species. Continuation of this activity is of vital importance to the conservation of bird species in this area. Data about nesting activities of select species recently helped guide decision making about when to suspend trail maintenance so as not to disturb nesting pairs.

The Southern Arizona Bird Observatory (SABO) in coordination with the BLM and the Friends of the San Pedro River also operates a banding station in the SPRNCA. Located in the ramada behind the San Pedro House, this banding station focuses on hummingbirds: their health, population size, and migration patterns. Banding sessions are open to the public. They are held 4 to 6 p.m. each Saturday during the summer; the last session is Oct. 5. See the Friends of the San Pedro River web site for more information about these popular events.

Recently, the BLM MAPS station in the SPRNCA has suffered from vandalism. This could have severe consequences for the health of bird species that live in and traverse our area. The detailed, long-term view of bird populations is key to understanding the impact of climate change, weather, urbanization, weather fluctuations, disease and other factors that impact avian species. The data collected is directly used to make sound decisions about how to manage the SPRNCA. No harm is done to the birds and if the motive of the vandalism is the desire to protect birds, it is badly misplaced.

Ron Stewart is a long-term local resident and retire employee of the U.S. Army who is currently Vice President of the Friends of the San Pedro River. As a Friends’ docent, Ron leads tours of historic sites in the SPRNCA. He is an amateur historian, archaeologist, and photographer. He also volunteers with Arizona State Parks and the National Park Service.

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