W. Scott Richardson Jean-Luc E. Cartron David J. Krueper Lauren Turner Thomas H. Skinner Chapter 3 The Status of the Cactus Ferruginous Pygmy-Owl in Arizona: Population Surveys and Habitat Assessment In 1993, the Arizona Game and Fish Department survey efforts and an increased number of cactus (AGFD) began formal population surveys in an at- ferruginous pygmy-owl detections, the Arizona popu- tempt to document the numbers and distribution of lation of cactus ferruginous pygmy-owls still appears cactus ferruginous pygmy-owls (Glaucidium brasil- small; 2) the currently known population of cactus ianum cactorum) in Arizona. Surveys were initiated to ferruginous pygmy-owls occurs chiefly in desertscrub gather information on this little-known subspecies habitats rather than riparian habitats reported in which was considered for listing at the time. Prior to historical accounts (see Chapter 2); 3) the population 1993, birders and avian biologists had conducted of cactus ferruginous pygmy-owls appears patchily many informal surveys in a sporadic and opportunis- distributed across suitable habitat with population tic fashion. However, the information derived from pockets occurring in northwest Tucson, southern those surveys was limited and often inaccessible, and Pinal County, the Altar Valley, Organ Pipe Cactus contributed little to the overall understanding of the National Monument, and the Tohono O’odham distribution and abundance of the species. From 1993 Reservation. to 1997, even the more formal cactus ferruginous In this chapter, we discuss some of the difficulties pygmy-owl surveys were limited in number and area and challenges of developing an effective and practi- covered and resulted in only a handful of cactus fer- cal survey protocol including results and insights ruginous pygmy-owl detections. With the listing of the from previous surveys. We then describe important cactus ferruginous pygmy-owl as an endangered spe- riparian and desertscrub habitats which represent cies, significantly more surveys were conducted in occupied cactus ferruginous pygmy-owl habitats or 1998 and 1999 by the AGFD, licensed consultants, habitats presumed suitable for cactus ferruginous land management agencies, and agency contractors. pygmy-owls. We then briefly describe initial agency The increased number of pygmy-owl detections during efforts to better characterize and describe suitable those two years resulted from this additional survey cactus ferruginous pygmy-owl habitat. Finally, we pre- effort. sent our recommendations for future survey efforts. While there is a considerable amount of potentially suitable cactus ferruginous pygmy-owl habitat that remains unsurveyed, we have learned the following 1. Survey Protocol _________________ information about the distribution of cactus ferrugi- In the last two decades, broadcast surveys have nous pygmy-owls within Arizona: 1) despite increased been promoted as a reliable and effective technique USDA Forest Service Gen. Tech. Rep. RMRS-GTR-43. 2000 27 to study the distribution and size of many small owl ability to detect an owl. Additionally, it has been populations (Johnson et al. 1981, Lynch and Smith suggested that, at least for the boreal owl (Aegolius 1984, McGarigal and Fraser 1985, Smith et al. 1987, funereus), the physiological state of individual owls, Ganey 1990, Stahlecker and Rawinski 1990, Noon et al. the amount of competition among males for nest 1992, Wauer et al. 1993). Because of the lack of ad- sites, and mating success can all influence rates of equate information regarding the numbers and distri- detection (Hayward et al. 1992). In Arizona, low popula- bution of cactus ferruginous pygmy-owls in Arizona, tion densities of cactus ferruginous pygmy-owls, and the AGFD developed a broadcast survey protocol as perhaps reduced competition for nest sites, may be they initiated formal cactus ferruginous pygmy-owl associated with lower rates of responsiveness. Thus, if population surveys in 1993 (Felley and Corman 1993). call points are too far apart and/or the time spent at This original protocol was developed based on the little each point is too short, some owls may escape detec- information known at that time about the biology of tion. The challenge has been to develop a protocol cactus ferruginous pygmy-owls and similar survey which balances the significant repercussions of not protocols employed for other small owl species. As detecting an owl, when it could potentially be im- surveys progressed and the effectiveness of the pro- pacted by some activity, with increased costs and tocol was evaluated, a revision of the AGFD protocol logistical difficulties resulting from a conservative took place in 1996 (Abbate et al. 1996). The 1996 survey protocol. Direct costs are associated with revisions included increasing the distance between actually conducting surveys; there are also indirect call points and increasing the amount of time spent at costs if the protocol results in the delay of project each call point. Other slightly different protocols were implementation. Another question considered is the utilized by contractors surveying for special projects in need for two protocols, one dealing with project clear- 1998. Adjustments to the original protocol were in ance and another for population assessment and re- response to changes in research objectives, manage- search activities. ment needs, and experience gained from previous In an effort to address issues regarding survey survey experience. protocol and associated management issues, the U.S. Protocol development attempts to maximize cactus Fish and Wildlife Service (USFWS) and the AGFD ferruginous pygmy-owl response to tapes by directing developed a survey protocol that was released for surveys to be performed during the highest known public comment in late 1998 (Appendix 3-1). This activity periods (i.e., dawn and dusk), and at the proposed survey protocol received significant review appropriate time of year (i.e., the courtship and nest- by a wide variety of public interests. Public comment ing season) (Gilman 1909, Terres 1991, Wauer et al. is currently being evaluated and a finalized protocol is 1993). There has been considerable discussion about expected sometime in 1999. While economic interests the effectiveness of surveys outside the peak breeding such as development, grazing, and mining may be best season. The original survey protocol defined a survey served by a stable protocol that can be considered in season extending from September to April (Felley and long-term planning efforts, the cactus ferruginous Corman 1993) but, while there appears to be some pygmy-owl survey protocol must be adaptive enough calling activity in the early fall, the vast majority of to incorporate advances in our understanding of this recent cactus ferruginous pygmy-owl detections have species. For example, it is only within the past two occurred during the spring courtship and nesting years that radio telemetry has been utilized to help us period, with a decrease in calling and responsiveness understand aspects of cactus ferruginous pygmy-owl observed through the remainder of the year (Richardson biology such as home range, territoriality, and habitat unpubl. data). use. Telemetry will also allow us to test responsive- Another debated issue has been the recommended ness of known owls to tape broadcasts. This new distance between calling stations for a survey. Results information must be utilized in order to develop the of initial response distance testing in Texas indicate most effective survey protocol. that owls will respond to a taped call from a distance of at least 700 m (Chapter 5). However, current proto- cols for surveying in Arizona recommend call point 2. Responses of other bird species to distances ranging from 150 m to 400 m. While shorter broadcast surveys _________________ distances between call points decrease survey cover- age and thus present some logistical and economic The ferruginous pygmy-owl is known as the “terror concerns, they do address reduced responsiveness or of small birdlife” (Sprunt 1955). Judging from the ability to detect owls because of local demographic numerous accounts describing the owl as mobbed by and physical factors. Many of the cactus ferruginous songbirds and hummingbirds (Gilman 1909, Sprunt pygmy-owls found in Arizona occur in urbanized 1955, Tyler and Phillips 1978, Abbate et al. 1996, areas with significant background noises from auto- Russell and Monson 1998), the occurrence of this owl mobiles, humans, dogs, etc. which reduce a surveyor’s is likely perceived as a threat by the local avifauna. 28 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-43. 2000 Mobbing is a behavior specifically directed against as the birds most often reacting to cactus ferruginous potential enemies during the reproductive season pygmy-owls (Abbate et al. 1996). In the Coronado Na- (Kruuk 1964, Hoogland and Sherman 1976, Shields tional Forest, where no pygmy-owl was found, several 1984) and raids of neighboring songbird nests by bird species responded with movement, vocalization, cactus ferruginous pygmy-owls have been documented and/or agitation during 1997 surveys (Table 3-2). Of in Texas and Arizona (see Chapter 1). Mobbing was these, however, only two identified species exhibited observed at all nest sites monitored in Arizona and agitated behavior and the bushtit (Psaltriparus involved a wide variety of species (Abbate et al. 1996, minimus) alone is a local year-round resident. Richardson unpubl. data). If bird