Christopher J. Norment

ON GRASSLAND BIRD CONSERVATION IN THE NORTHEAST

Populations of many grassland birds in North America have declined significantly during the last 30 years (Knopf 1994, Peterjohn and Sauer 1999). Although population trends of many groups of breeding birds vary across geographic regions (James et al. 1992, Herkert 1995, Sauer et al. 1997), the declining trend for grassland birds is consistent across much of North America, including the Northeast (Bollinger and Gavin 1992, Askins 1993, Peterjohn and Sauer 1999). Declining trends and relatively low population levels for many grassland birds in the Northeast (Shriver et al. 1997), defined here as New York and the six New England states, has led to concern for the status of many species. By the early 1990s, birds of grassland and open habitats were the species most frequently listed as endangered, threatened, or of special concern by states in the Northeast, with 12 species classified by three or more states (Vickery 1992). Reasons for grassland bird decline in the Northeast include farmland abandonment with subsequent succession to woodland habitat, decline of hayfield area, and increased haycropping during the nesting season (Andrle and Carroll 1988, Bollinger et al. 1990, Askins 1997, Vickery and Dunwiddie 1997). Because many grassland bird species are area-sensitive, those species are particularly vulnerable to habitat loss and fragmentation (Herkert 1994, Vickery et al. 1994). In New England and New York, grassland area has declined by 60% since the 1930s (Vickery et al. 1994). Concern for grassland birds in the Northeast has stimulated research, educational initiatives, conservation-oriented management, and habitat acquisition by federal, state, and nongovernmental organizations (Vickery et al. 1994, Jones and Vickery 1997, National Resources Conservation Service 1997, Shriver et al. 1997, Vickery and Dunwiddie 1997, Casey 1998). However worthwhile those activities may be, they have occurred without a comprehensive regional plan for managing grassland birds. Such a regional plan, preferably as part of a general plan for all native birds in the region, is crucial for several reasons. First, the plan would provide a rationale for conserving grassland birds in the Northeast in the context of current and historical land-use patterns.

Demographic characteristics of a Grasshopper Sparrow population in a highly fragmented landscape of western New York state

Abstract We studied the breeding biology, site fidelity, and dispersal of Grasshopper Sparrows (Ammodramus savannarum) from 1996 to 2000 in a fragmented landscape in western New York State. Ten fields (1.8–13.2 ha) contained territorial male Grasshopper Sparrows during the study; total territorial males in the study area varied between 31 and 19 birds. In 1996, eight fields were occupied; five extinctions and two colonizations occurred between 1997–2000. Fields that suffered extinctions were smaller than fields in which subpopulations persisted or colonizations occurred. Adult return rates (0.33 vs. 0.16), nest success (0.59 vs. 0.25) and average number of fledglings/female/year (2.3 vs. 1.3) tended to be higher in fields ≥8 ha. Estimates of λ, the finite rate of increase, were 0.23 for small fields and 0.46 for large fields. Although sample sizes were small, our data suggest that return rates and productivity were greater in large than in small habitat patches. However, even the larger habitat patches in our study area appeared to function as population sinks, suggesting that the Grasshopper Sparrow population is unlikely to persist without immigration. Survival prospects for our study population are poor, given its demographic characteristics and the fragmented nature and continuing loss of grassland habitat. Our results suggest that conservation efforts in the Northeast should focus on protecting large patches of continuous grassland habitat.

EFFECTS OF PLOT SIZE AND HABITAT CHARACTERISTICS ON BREEDING SUCCESS OF SCARLET TANAGERS

We studied the effects of forest patch size and habitat characteristics on breed- ing success of Scarlet Tanagers (Piranga olivacea) in western New York in 1995 and 1996. Twenty forest stands were grouped into four size classes: Group I ( 50 to 150 ha, n = 5), and Group IV (>1,000 ha, n = 2). Group I, II, and III sites were habitat patches located in fragmented landscapes, whereas Group IV sites were located in continuous forests. Although densities of male tanagers were similar in Group II, III, and IV sites, tanagers were absent from all forest patches smaller than 10 ha. Territory size did not differ among males in Group II, III, and IV sites. Pairing success exceeded 75% in all forest size classes in 1995 and 1996, and 100% of the observed males were paired in continuous forest sites. Pairing success differed significantly among forest size classes in 1995 and approached significance in 1996. Fledging success increased significantly with area and was highest (64%) in continuous forest sites. Stepwise multiple regression and principal components analysis indicated that male tanagers breeding in for- est patches with higher canopy cover and lower density of oaks had higher pairing success than males in patches with lower canopy cover and higher density of oaks, and that males breeding in larger forest patches with more surrounding forest cover had higher fledging success than males in small patches with less surrounding forest cover. Our results indicate that: (1) breeding density is not a good indicator of habitat quality for forest-interior Neo- tropical migrants, and (2) large tracts of continuous forest are important for maintaining populations of these species. Received 19 March 1997, accepted 5 May 1998.

Influence of habitat structure and fruit availability on use of a northeastern stopover site by fall songbirds

Abstract Many studies have suggested that early successional habitats are important for fall migrant and resident birds. In light of this, we studied habitat relationships, preferred fruiting shrub species, and fruit consumption by birds in early successional habitats during the fall at Iroquois National Wildlife Refuge, Alabama, New York, USA. We used transects to count birds in 12 shrub and 6 early successional forest sites during 2008–2009, and collected data to construct habitat models. We examined frugivory using a paired open/enclosed fruit branch experiment and by analyzing fecal samples of birds captured in mist nets. More fall songbirds were detected in shrublands than in forests across the 2 years, although forests with well-developed understories also had high detection levels. Total bird abundance was positively related to fruiting species richness and negatively related to small woody stem (0.0–2.5 cm) abundance. Abundance of American Robins (Turdus migratorius) was positively related to total shrub cover and fruit abundance on common buckthorns (Rhamnus cathartica), and negatively related to small and large (2.5–8.0 cm) stem abundance. Abundance of Gray Catbirds (Dumetella carolinensis) was positively related to fruiting shrub species richness. Abundance of Song Sparrows (Melospiza melodia) was positively related to gray dogwood (Cornus racemosa) fruit abundance, and negatively related to small stem abundance and bella honeysuckle (Lonicera × bella) fruit abundance. Fecal analysis suggested that birds as a whole disproportionately consumed fruit species relative to availability, and consumed more bella honeysuckle and common buckthorn than gray dogwood. Fewer fruits remained on open branches than enclosed branches, suggesting birds actively consumed fruits at our sites. Our results suggest that fall migrant and resident songbirds as a whole benefit more from mature shrublands that contain a diversity of fruiting shrub species than from early successional forests. While these characteristics may benefit the suite of fall migrants and residents at our location, appropriate habitat management may differ for other locations or migratory species.

Evaluation of a reproductive index for estimating productivity of grassland breeding birds.

ABSTRACT. Declining populations of grassland breeding birds have led to increased efforts to assess habitat quality, typically by estimating density or relative abundance. Because some grassland habitats may function as ecological traps, a more appropriate metric for determining quality is breeding success, which is challenging to determine for many cryptic-nesting grassland birds. This difficulty led Vickery et al. (1992) to propose a reproductive index based on behavioral observations rather than nest fate. We rigorously evaluated the index for 2 years using a Savannah Sparrow (Passerculus sandwichensis) population in western New York and found a weak correlation in classification of the breeding stages of monitored territories among multiple observers (r = 0.398). We also discovered a large difference between overall territory and nest success rates independently estimated with the index (9.8% over the entire breeding cycle) and with nest searching and monitoring (41.7% of nests successfully fledged young). Most importantly, we made territory-level comparisons of index estimates with actual nest fate and found that the index correctly predicted fates for only 43% of the monitored nests. A Mayfield logistic regression analysis demonstrated that only index rank 4 (eggs hatched, but young failed to fledge) showed a strong positive correlation with nest success. Although the reproductive index may function as a coarse indicator of habitat suitability (e.g., documenting production in potential ecological traps), in our study the index exhibited neither internal consistency nor the ability to predict nest fate at the plot or territory level and functioned poorly as a substitute for nest searching and monitoring.

Use of Hair Tubes to Detect Small-Mammal Winter Activity in a Northern Forest Habitat

Abstract We used hair tubes to examine the winter activity of small mammals in relation to coarse woody debris and snow cover in a deciduous forest woodlot in western New York State during the winters of 2006 and 2007. Hairs trapped on sticky tapes in baited hair tubes were used to identify mammal species. During the winter of 2006, a higher proportion of baits was removed from hair tubes sites 2 m away from logs, relative to hair tubes adjacent to logs, while significantly more baits were removed from hair tubes adjacent to logs in 2007. A significantly greater proportion of baits was removed from log and open sites combined in 2006 than in 2007. However, in 2007, a higher proportion of hair tubes with baits removed also had mammal hairs on their tapes. The higher proportion of baits removed from hair tubes in 2006, and the increased proportion of baits removed from sites near logs in 2007, was most likely due to reduced snow cover in 2006. Hair tubes offer several advantages relative to live traps in the study of winter small-mammal activity. They are simple to use, do not require handling animals, eliminate trap-related mortality, and can be used at any spatial scale, including the landscape level. Finally, they employ low-cost materials, and can be adapted to a range of conditions and target species.

Nocturnal activity and energetic condition of spring landbird migrants at Braddock Bay, Lake Ontario

Abstract We investigated the relationship between migratory restlessness and stored energy reserves in two species of landbird migrants at Braddock Bay, Lake Ontario during spring 1999 and spring 2000. There was no significant difference in the amount of nighttime locomotor activity between lean and fat Swainsons Thrushes (Catharus ustulatus) or White-throated Sparrows (Zonotrichia albicollis) held overnight in activity cages. We found no significant relationships between nocturnal activity level and energetic condition (mass/wing chord) or date of capture. In addition, there were no significant differences in nocturnal activity levels between age groups in Swainsons Thrushes. These results suggest that the migratory restlessness of spring migrants stopping at this site is not strongly influenced by their energetic condition upon arrival, regardless of age or date of passage. Birds nearing the end of their spring migratory route that are very close to their breeding grounds may show decreased levels of migratory restlessness and short stopover durations, independent of energy reserves. When stopping at northerly sites, spring migrants may therefore display distinct differences in stopover behavior and requirements compared to sites used earlier along the spring migratory route.

Absence of breeding readiness in neotropical and long-distance migrant landbirds during spring stopover

We investigated breeding readiness of selected migrant species captured at a known stopover site in western New York during the spring of 1995 and 1996. A total of 775 individuals representing 14 species were examined for outward physiological indication of male breeding readiness measured by relative size of cloacal protuberance. Only of the 775 individuals exhibited a cloacal protuberance, hoth being captured in 1996; one Ruby-crowned Kinglet (Regulus calendula) and one Swainsons Thrush (Catharus minimus). Cloacal lavage samples were taken from 22 White-throated Sparrows (Zonotrichia albicollis) and 26 Swainsons Thrushes during the spring of 1996. None of the migrating individuals lavaged exhibited presence of cloacal sperm regardless of species, sex, time, or date of capture. Poor energetic condition was typical of these captured migratory landbirds. Depleted energetic stores may explain the lack of early sperm production in migrants at this stopover site.

What is the Best Available Science?: Conservation Status of Two California Desert Vertebrates

Scientific progress depends on evidence-based research, and reliance on accurate scholarship is essential when making management decisions for imperiled species. However, erroneous claims are sometimes perpetuated in the scientific and technical literature, which can complicate policy and regulatory judgments. The literature associated with two enigmatic California desert vertebrates, the Panamint alligator lizard Elgaria panamintina and the Inyo Mountains salamander Batrachoseps campi, exemplifies this problem. We produced a comprehensive threat analysis and status assessment for these species, which are both under review for possible listing under the US Endangered Species Act (ESA). Despite uncertainties and limited data, we find that many sources contain factual errors about the status of these two species, particularly the original petition that advocated for ESA listing. Although localized declines may have gone undetected, no evidence exists of population declines, population extirpation, or population-scale habitat conversion for E. panamintina. However, there is evidence of recent flash flood damage to some occupied B. campi habitat, which has possibly led to population declines at those localities. Contrary to inaccurate statements by some authors, all known populations of both species occur exclusively on federal lands, and numerous populations have likely benefited from recent federal management targeted at reducing known threats. Of the 12 threats that we identified for one or both species, only three currently appear to be serious: water diversions, climate change, and flash floods. The remaining threats are neither widespread nor severe, despite numerous contrary yet poorly supported statements in the literature. We thus evaluate the contemporary conservation status of both species as relatively secure, although B. campi is more at-risk compared to E. panamintina. This conclusion is independently supported by a recent review. Nonetheless, ongoing stewardship of these species in a multi-use context by federal agencies remains vital, and we identify several priority management actions and research needs for both species. We also recommend updated determinations on the IUCN Red List, and the Species of Conservation Concern list of the Inyo National Forest. To maximize the quality and effectiveness of conservation planning, we urge government agencies, non-governmental organizations, and individual scientists to maintain high standards of scholarship and decision-making.

Sabine's Gull (Xema sabini) Nesting Aggregations in Western Alaska

Abstract We analyzed data on the size of nesting aggregations of Sabines Gulls (Xema sabini) observed in the Yukon–Kuskokwim Delta (YKD), Alaska, between 1986 and 2013, to determine whether the species is a “solitary low-density nester” there, as in other parts of its range. Data for 1087 nests show that 56% of Sabines Gull nests were solitary and that <3% of aggregations exceeded 10 nests, although factors positively correlated with the evolution of colonial nesting, including exposure of nests to predators, aquatic habitat, and absence of feeding territories, apply to Sabines Gulls nesting in the YKD. Although Sabines Gulls in the YKD were most often solitary nesters, in 2010 we found a 102-nest aggregation on a small island in the study area, larger than any reported for the species. Among all aggregated nests, 75.4% occurred on islands, and only 13.9% along shorelines, while 39.8% of all solitary nests occurred on islands, and 39.3% along shorelines. The proportion of Sabines Gull nests in the YKD located on islands ranged from 0.15 (in 1991) to 0.78 (in 2010) and showed no significant trend between 1986 and 2013, despite an increase in population size during the period. Although islands may provide greater protection from mammalian predators, and the majority (54.6%) of Sabines Gull nests in our study area occurred on islands, thousands of similar, apparently suitable islands remained unoccupied by Sabines Gulls and other nesting species every year. Given the potential benefits of nesting on islands, in colonies, or in colonies on islands, the YKD Sabines Gull population maintains considerable behavioral variability, in terms of nest-site selection and size of nesting aggregations, perhaps to take advantage of locally abundant food resources.