SANDHILL CRANE ABUNDANCE AT GRAYS LAKE, IDAHO

We initiated a study on the breeding ecology of greater sandhill cranes (Grus canadensis tabida) in the Grays Lake basin ofIdaho in 1997. Interest in the status of crane populations at Grays Lake is high; consequently, we present preliminary information on estimated size of the population, changes since the 1970s, and potential environmental factors involved. Drewien (1973) counted an average of549 cranes in the spring and estimated 250 nesting pairs in 1970-71. Number of nesting pairs reportedly increased 33% (to 332) by 1982 in response to intensive management, then declined 40-60% by 1996 (Drewien 1997, and Homocker Wildlife Institute, personal communication). During 1998-99, spring counts averaged 736 cranes (34% increase from 1970-71). Among 44 survey units that were searched during both studies, nest densities increased in 27, decreased in 13, and remained unchanged in 4. Nest success declined from 78% in 1970-71 to 59% in 1997-99. We estimated that renesting accounted for 10% of nests in 1999. Fall staging populations were similar between the early 1970s (n = 1313) and late 1990s (n = 1370), but well below peak counts of the 1980s (often \u3e3000). Factors potentially influencing the crane populations at Grays Lake include habitat management, climate (drought), predator populations, manipulation of marsh water levels, agricultural practices, baiting, and disturbance

NESTING ECOLOGY OF SANDHILL CRANES AT GRAYS LAKE, IDAHO

We examined the nesting ecology of greater sandhill cranes (Grus canadensis tabida) at Grays Lake, Idaho during 1997-99 to detennine the effects of nest-site characteristics and land use on crane nest success. These are preliminary results from 3 years of a 4-year study. Crane nests were located in portions of the Grays Lake basin from early May through late June each year (n = 131 in 1997; n = 131 in 1998; n = 143 in 1999). Apparent nest success varied among years (54% in 1997, 71% in 1998, and 53% in 1999; overall average of 59%). We estimate that 10% of nests found in 1999 were renests. Most crane nests were located in baltic rush/spikerush (Juncus balticus/Eleocharis sp.; 46% of nests), semi-wet meadow (19%), and bulrush/cattail (Scirpus sp./Typha sp.; 19%) plant communities; 62% of nests during early May were in:;; 12 cm of water. As indicated by plant community, water depths at nests, and nest isolation rankings, nest success tended to be higher where nests were in relatively deep water (ca. \u3e40 em) and were relatively isolated from access by mammalian predators. Nest success rates during 1997-99 were lower than those recorded in 1950-51 (90%, n = 107; Steel 1952) and 1970-71 (78%, n = 308; Drewien 1973). A variety offactors likely contribute to lower nest success, including changing predator communities over the past 30-40 years. Differences among years in our study may be affected by changing availability of alternate prey. Small mammal populations and crane nest success were the highest in 1998. Water-level management, relating to cranes and other waterbird populations, plant communities, and ecosystem function, is an emerging issue for land managers in the Grays Lake basin

Distribution and Trends of Endemic Hawaiian Waterbirds

Four endemic species of wetland-dependent waterbirds occur on the main Hawaiian Islands, all of which have experienced sharp population declines and are listed as endangered species. Twice per year, state-wide surveys are conducted to count waterbirds, but these surveys are evaluated only infrequently. We used a state-space approach to evaluate long-term (1986–2016) and short-term (2006–2016) trends and current distribution and abundance of endemic Hawaiian waterbirds. The most numerous species was the Ae‘o, or Hawaiian Stilt (Himantopus mexicanus knudseni), with a 5-year estimated average abundance of 1,932 individuals, followed by ‘Alae Ke‘oke‘o, or Hawaiian Coot (Fulica alai), with 1,815 individuals, Alae ‘Ula, or Hawaiian Common Gallinule (Gallinula galeata sandvicensis) with 927 individuals, and the Koloa Maoli, or Hawaiian Duck (Anas wyvilliana) with 931 individuals. All four species had positive trends over the long-term, but short-term and island specific trends were more variable, and in some cases negative. These results provide valuable information to help guide management of Hawaii’s threatened and endangered endemic waterbirds

Sandhill Crane Abundance and Nesting Ecology at Grays Lake, Idaho

We examined population size and factors influencing nest survival of greater sandhill cranes (Grus canadensis tabida) at Grays Lake National Wildlife Refuge, Idaho, USA, during 1997–2000. Average local population of cranes from late April to early May, 1998–2000, was 735 cranes, 34% higher than that reported for May 1970–1971. We estimated 228 (SE = 30) nests in the basin core (excluding renests), 14% higher than a 1971 estimate. Apparent nest success in our study (x = 60%, n = 519 nests) was lower than reported for Grays Lake 30–50 years earlier. Daily survival rates (DSRs) of all nests averaged 0.9707 (41.2%). The best model explaining nest survival included year and water depth and their interaction. Nest survival was highest (DSR = 0.9827) in 1998 compared with other years (0.9698–0.9707). Nest survival changed little relative to water depth in 1998, when flooding was extensive and alternative prey (microtines) irrupted, but declined markedly with lower water levels in 2000, the driest year studied. Hypotheses relating nest survival to vegetation height, land use (idle, summer grazing, fall grazing), and date were not supported. In a before-after-control-impact design using 12 experimental fields, nest survival differed among years but not among management treatments (idle, fall graze, fall burn, and summer–graze–idle rotation), nor was there an interaction between year and treatments. However, DSRs in fall-burn fields declined from 0.9781 in 1997–1998 to 0.9503 in 1999–2000 (posttreatment). Changes in the predator community have likely contributed to declines in nest success since the 1950s and 1970s. Our results did not support earlier concerns about effects of habitat management practices on crane productivity. Nest survival could best be enhanced by managing spring water levels. Managers should continue censuses during late April to evaluate long-term relationships to habitat conditions and management