1996 Idaho Bald Eagle Nesting Report

Authors(s): J. Beals and W. Melquist

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Publication Date: 0000-00-00

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Abstract: This report summarizes the 1996 bald eagle (Haliaeetus leucocephalus) nesting survey for Idaho. The nesting population of bald eagles in Idaho continues to increase. There were 104 territories monitored in 1996. Eleven new territories were documented during the nesting season resulting in 90 occupied territories statewide. Twenty-seven percent of the occupied territories were unsuccessful. The remaining nesting pairs successfully fledged 92 young. The number of young fledged per occupied territory was 1.02 in 1996, and the number of young fledged per successful pair was 1.44. INTRODUCTION Bald eagles nest in three primary areas within Idaho. The largest nesting population is found in eastern Idaho along the North and South Forks of the Snake River. The second largest nesting population is located within the Pend Oreille River drainage and the Kootenai valley of north Idaho. The North Fork of the Payette River near Cascade Reservoir contains the third concentration of nesting bald eagles. Other territories are scattered throughout southwestern and south-central Idaho. Bald eagle recovery in Idaho is assessed in terms of 10 management zones as outlined within the Pacific Bald Eagle Recovery Plan (1986). Some management zones are shared with surrounding states. This report summarizes only the Idaho portions of those zones. The objectives of annual nesting bald eagle surveys are: Determine the productivity of breeding pairs at all occupied bald eagle territories in Idaho. Compile nesting data and other information for the purpose of monitoring bald eagle recovery in Idaho. Document and map the locations of new bald eagle territories and new nests within existing territories. METHODS Aerial, ground, and float surveys were used to collect nesting data on eagles. Occupied territories (pair of eagles present) with known outcome were surveyed at least twice. The first survey, generally during March, was conducted to determine occupancy. Occupied territories were surveyed again when the nestlings were within approximately one to two weeks of fledging (late June to mid-July) to determine productivity (the number of successful pairs and the number of near fledging-age young) (Steenhof 1987). Nests were occasionally checked at other times, with pertinent information recorded on nest observation forms. When possible, nestling bald eagles were banded with USFWS aluminum leg bands and plastic color-coded leg bands in the Idaho portion of the Greater Yellowstone Ecosystem by Whitfield et al. (1996) as part of a larger, on-going research project. RESULTS One hundred four bald eagle nest sites were checked in 1996, 90 of which were occupied (Table 1). Of the 90 occupied nest sites, 11 were new territories. The status and productivity of individual bald eagle nesting territories for 1996 are summarized in Table 2. Twenty-seven percent of occupied bald eagle nests were unsuccessful in 1996 (Table 1). Ninety-two young reaching fledging age were produced in the remaining nests, resulting in an average of 1.44 young per successful pair (Table 1). Zone Narratives Zone 7 Twenty-five occupied nesting territories were monitored in Zone 7 during 1996 (Table 2), three of which were classified as new territories. These new territories were located on the Clark Fork River, Lake Pend Oreille and on the Kootenai River. All three new territories successfully fledged young in 1996 (Table 2). An average of 1.5 young were produced from 19 successful nests. Twenty-eight young fledged from nests within the zone. A single bald eagle mortality was documented at Powder Horn. Chemical analyses of the carcass are being conducted as part of an ongoing, environmental contaminant investigation (Audet, pers. commun.). Zone 14 The Dry Gulch and Lone Pine nests were unoccupied in 1996. Zone 15 Seventeen territories were monitored in Zone 15 during 1996. Fifteen of those nest sites were occupied, including 5 new territories (Table 2). A new territory was established near Challis although the nest was abandoned prior to egg-laying. A new pair of eagles on Deadwood Reservoir successfully fledged 2 young. A new territory located in High Valley successfully fledged 1 young. A new territory located on Payette Lake was unsuccessful in 1996; the nestling was found dead at the base of the nest tree. A new territory was documented near McCall airport in 1996. The active nest was previously thought to be an alternate nest site for the Hait Ranch territory. According to Norm Nelson, this nest site has been active since 1991 (Nelson pers. commun.). An average of 1.5 young were produced from 11 successful nests. Sixteen young fledged from nests within the zone. The Cabarton nest was reoccupied in 1996, but was unsuccessful. The Donnelly nest was also unsuccessful in 1996. A single bald eagle mortality was documented in Zone 15 during 1996. A banded eagle (left leg/629-37944, right leg/orange 3G) was electrocuted approximately 38 miles SE of Salmon, Idaho. Zone 16 Five nest sites were monitored within this zone in 1996, 4 of which were occupied (Table 2). Four young were known to have fledged from Zone 16, resulting in an average of 1.6 young per successful pair. The Powerline nest has not been located for two years, but adults and an unconfirmed number of young were observed in the vicinity in 1996. The Lake Lowell nest, successful for the first time in 4 years, fledged 2 young. The Montour nest was unoccupied in 1996. No bald eagle mortality was documented for Zone 16 during 1996. Zone 17 The Silver Creek nest constructed in 1994 was reoccupied by a pair of eagles in 1996. The nest was abandoned during the incubation period. No bald eagle mortality was documented for Zone 17 during 1996. Zone 18 Forty-five nest sites were monitored within Zone 18 in 1996 (Table 2) (Whitfield et al. 1996). Forty-three nest sites were occupied. Three new breeding territories were discovered in 1996; two were located on the South Fork of the Snake River and another on Ririe Reservoir. An average of 1.5 young were produced from 29 successful nests. Forty-three young fledged from nests within the zone. Sixteen nestlings were banded within the Idaho portion of the Greater Yellowstone Ecosystem (Whitfield et al. 1996). No bald eagle mortality was documented for Zone 18 during 1996. Zone 20 Four of 6 nest sites in Zone 20 were monitored in 1996. Two were occupied, but only 1 (Ferry Butte) was successful. Two young were produced from Zone 20 in 1996. The Old Fort Hall and the McTucker nests were not monitored during 1996. The Blue Lakes CC and Milner Dam territories were unoccupied in 1996. No bald eagle mortality was documented in Zone 20 during 1996. Zones 8, 19, & 37 No territories were documented within Idaho for these zones. DISCUSSION Idaho's bald eagle population continues to increase (Table 3). Statewide productivity in terms of young per occupied territory and young per successful nest declined slightly in 1996, but has remained relatively stable since monitoring began in 1979. Zone 20 had the greatest nest success at 2.0 young per successful nest; however, only one nest was known to have successfully fledged young (Table 1). Bald eagle recovery in Idaho appears to be on track with recovery population goals (RPG) established in the 1986 Pacific Bald Eagle Recovery Plan (Table 4). Two of the 3 management zones exclusive to Idaho (Zones 15, 17, and 20) have exceeded RPGs. Zone 17 has an RPG of 1 and contained 1 unsuccessful territory in 1996. Zone 20 (RPG=0) contained 2 occupied territories in 1996. Zones 7, 8, 18, and 19 have also exceeded RPGs, although Zones 8 and 19 have no documented nests in Idaho. Occupied nests within Idaho contribute 36% and 86% of the RPG for Zones 7 and 18, respectively. No occupied nests were documented within Zone 14, although 2 inactive nest sites have been monitored annually (Table 2). Zone 16 had 4 occupied territories in 1996 and a RPG of 5. Zone 37 has a RPG of 0 and no documented nesting. As Idaho's bald eagle population continues to increase, continued thorough and systematic surveys are needed to ensure that the population and recovery are adequately monitored. Zone coordinators should continue to send the results of nesting surveys to Wayne Melquist, State Nongame Manager, IDFG, PO Box 25, Boise ID, 83707. It is important that bald eagle territories be identified by their number, which reflects the zone, territory within the zone, region within the zone, and any alternate nests within the territory. It has become increasingly important to completely document all alternate nests within territories. Contact Wayne Melquist to obtain the appropriate nest record and survey forms. Finally, if zone coordinators are unable to monitor all of the nests within their zones, please inform Wayne Melquist so that arrangements can be made to check on those nests. LITERATURE CITED Steenhof, K. 1987. Assessing raptor reproductive success and productivity. Pages 157-170 in B.A. Giron Pendleton, B.A. Millsap, K.W. Kline, and D.M. Bird, Eds. Raptor Management Techniques Manual, Chapt. 9. Natl. Wildl. Fed., Sci. and Tech. Series No. 10, Washington, D.C. U.S. Fish and Wildlife Service. 1986. Recovery plan for the Pacific bald eagle. U.S. Fish and Wildl. Serv., Portland, OR. 160 pp. Whitfield, M., M. Maj, A. Whitfield, J. Naderman, J. Gardetto, K. Rice, D. Trochta, R. Welch, B. Aber, and B. Alford. 1996. Annual bald eagle productivity, final report, 1996. Idaho portion of the Greater Yellowstone Ecosystem. Greater Yellowstone Ecosystem bald eagle research project. Unpublished report. 23 pp.

Keywords: Idaho, animal, bird, Aves, ornithology, eagle, bald eagle, Haliaeetus leucocephalus, nest, nesting, population, mortality, breeding, habitat, management, banding, Greater Yellowstone Ecosystem