Library Search

Different types of human activity may influence raptors in various ways, potentially affecting their abundance, distribution, habitat use and productivity. We studied the effects of recreational trails on wintering raptor populations in grasslands of eastern Boulder County, Colorado, from December 1995-March 1996. We conducted strip transects to survey raptor populations at six study sites. All sites consisted of short and/or tallgrass prairie, and all contained a riparian corridor. Three sites contained recreational trails running adjacent to the riparian corridor (trail), while three sites contained no trails (control). Species richness, abundance and perch use were compared between control and trail sites. Species richness was consistently greater in control sites. Abundance of total raptors observed was greater in control sites. Abundance of Bald Eagles (Haliaeetus leucocephalus) was greater in control sites, while abundance of Red-tailed Hawks (Buteo jamaicensis) was similar for control and trail sites. Perching distances from riparian corridors were greater in trail sites than in control sites. In addition, raptors perched along riparian corridors more frequently in control sites. Results of this study suggest that recreational trails may have affected habitat selection of some raptor species in this grassland ecosystem.

In conjunction with release of a final environmental assessment of this action, the U.S. Fish and Wildlife Service (??we?? or ??the Service??) is finalizing permit regulations to authorize limited take of bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) under the Bald and Golden Eagle Protection Act (Eagle Act), where the take to be authorized is associated with otherwise lawful activities. These regulations also establish permit provisions for intentional take of eagle nests under particular, limited circumstances.

Monitoring of raptors is a critical component of the MSCP. This project, specifically, addresses monitoring the raptor species identified as target species for MSCP monitoring with one exception--the Burrowing Owl (BO; Athene cunicularia hypugaea). In addition to the Burrowing Owl, the MSCP Biological Monitoring Plan (Ogden, 1996) identified the following raptor species (hereafter referred to as the “target” species) to be monitored: Golden Eagle (GE; Aquila chrysaetos), Bald Eagle (BE; Haliaeetus leucocephalus), Peregrine Falcon (PF; Falco peregrinus), Northern Harrier (NH; Circus cyaneus), Ferruginous Hawk (FH; Buteo regalis), Swainson’s Hawk (SH; Buteo swainsoni), and Cooper’s Hawk (CH; Accipiter cooperii). Prior to the subject work, no comprehensive study had been conducted for any of these species, within the geographical limits of the MSCP. The original project objectives (taken from the contract's scope of work) are as follows: -Determine where breeding and wintering individuals (of the target species) are located within the study areas. -Wherever possible, document the breeding success of active pairs. -Characterize situations of both successful and less successful or unsuccessful habitat. -Identify, modify, or create, if necessary, survey raptor monitoring methods, based on scientific principles that would be appropriate to meet the objectives of the MSCP Monitoring Plan. -Identify management, including research, needs and enhancement opportunities.

A 3-year raptor study was initiated by the County of San Diego Department of Parks and Recreation (DPR) to collect baseline information on eagle and other raptor activity at the Preserve. Raptor foraging surveys and golden eagle nest monitoring was conducted by AECOM at the Preserve from September 2013 through August 2014 on behalf of the County DPR. AECOM worked in partnership with the U.S. Fish and Wildlife Service to complete these surveys. This report summarizes the results of Year 1 (September 2013 through August 2014) of the 3-year study. AECOM will continue surveys for Year 2 and Year 3.