Bird surveys and habitat assessments along the Aros-Yaqui river corridor on and around the Northern Jaguar Reserve

Report for Northern Jaguar Project and Naturalia A.C.

Ten years ago, two conservation organizations, Naturalia and Northern Jaguar Project, began purchasing private ranches in a remote region of northwest Mexico in an effort to protect the largest remaining population of breeding jaguars (Panthera onca) in northwest Mexico. Since that time, the reserve has grown to 20,140 ha and its mission has broadened to focus more generally on biodiversity conservation in this wild region. Today, the Northern Jaguar Reserve (NJR) is the only reserve in Mexico that protects large areas of Foothills (Sinaloan) Thornscrub. Foothills Thornscrub is the dominant vegetation community in the foothills and valleys west of the northern Sierra Madre Occidental and forms a broad transition zone between tropical and temperate environments. The NJR is situated near the northern extent of Foothills Thornscrub, directly west of the northern end of the Sierra Madre Occidental. It is surrounded on three sides by deep, lowland canyons of the lower Río Aros and upper Río Yaqui, which includes the largest remaining section of free-flowing river in northwest Mexico. Due in part to its ruggedness and inaccessibility, this region is among the largest and least fragmented wildlands in northwest Mexico.

There have been few efforts to describe the fauna and flora of this remote region but birds are one of the better studied groups. Thomas Clark (1984) reported notable observations of birds near Sahuaripa in April and May 1978 and Steve Russell (Russell and Monson 1998) worked in the high mountains east of Sahuaripa in March 1984. Bryan Brown studied nesting Bald Eagles (Haliaeetus leucocephalus) along the Río Aros, Bavispe, and Yaqui (Brown and Warren 1985, Brown 1988), but it was not until 1998 when important observations of species other than raptors (Rodríguez-Estrella and Brown 1990) were reported (Russell and Monson 1998). More recently, in July and August 2005, biologists from the University of Arizona recorded 80 species of birds along a 185 km stretch of the Río Aros below Natora and Río Yaqui above Sahuaripa (O’Brien et al. 2006). In April 2007, Peter Warshall and others visited several portions of the Northern Jaguar Reserve and recorded 99 species including a variety of Neotropical migratory species (Warshall 2007). Most recently, between summer 2007 and spring 2010 (Flesch 2008, 2009, 2010), Flesch and others described the distribution and abundance of birds across the NJR; in April 2011, Flesch and Jacobs surveyed birds along the Aros-Yaqui corridor and summarized baseline data on migratory birds.

As part of a broader effort to document the region’s biodiversity and help guide conservation efforts in the region, we studied avifauna on and around the Northern Jaguar Reserve in 2011 and 2012. Extensive previous efforts between 2007 and 2011 were successful in documenting the distribution, abundance, and seasonal and breeding status of birds across much of the reserve (see Flesch 2008, 2009, 2010), thus we focused our efforts on describing the distribution and abundance of birds and presence and condition of habitat for breeding and migratory birds in inaccessible areas on the reserve and in the region immediately surrounding the reserve. Because birds are excellent indicators of environmental conditions, our efforts are important for guiding Naturalia and Northern Jaguar Project in developing conservation proposals and priorities related to reserve expansion and management. Because much of the region is roadless, extremely rugged, and accessible only from Aros-Yaqui river corridor, we organized two river-based expeditions and surveyed areas along the river and in major tributaries and side canyons. Here, we describe summer and wintering bird communities along the Aros-Yaqui river corridor and habitat conditions in the region. During the summer expedition, we invited a mammalogist (David Parsons) and herpetologist (Robert Villa) to participate, and they provided information on these taxa that we report here.