Kenneth F. Abraham

PERFORMANCE OF A GPS ANIMAL LOCATION SYSTEM UNDER BOREAL FOREST CANOPY

An automated animal location system, based on Global Positioning System (GPS) technology, is being used for wildlife research. The GPS is a divergent technology, and positional accuracies vary between millimeters and tens of meters, depending on the system used and operating conditions. Before GPS-based tracking data can be used for habitat analyses, the influence of habitat on GPS-collar performance must be evaluated under various canopy conditions, including the optimal condition of no canopy. We evaluated performance of nondifferentially corrected GPS collars in an experimental forest with mature, evenly spaced trees and on wild free-ranging moose (Alces alces) to determine the influence of canopy on positional accuracy and observation rate. In an experimental forest with mature, evenly spaced trees (henceforth called spacing trial), canopy characteristics of tree species, spacing, height, basal diameter, and canopy closure had no influence on positional accuracy (P > 0.05), but had an influence on GPS observation rate (P < 0.001). Location error was greater if positions were based on 2-dimensional rather than 3-dimensional mode of operation (P < 0.001), with location errors of 65.5 and 45.5 m, respectively. Location error in 3-dimensional mode did not differ from the expected error of 40 m (P = 0.43). As tree density increased, observation rate decreased and the probability of the GPS receiver operating in 2-dimensional mode increased (P < 0.001), resulting in increased location error. With future development of differentially corrected GPS collars, location errors of <10 m are expected. J. WILDL. MANAGE. 59(3):543-551

Lower Predation Risk for Migratory Birds at High Latitudes

Predator Avoidance Strategy Selective pressures influencing bird migration can include availability of food, pressure from parasites and pathogens, and predation risk. The importance of the last of these is revealed by McKinnon et al. (p. 326; see the Perspective by Gilg and Yoccoz), who present an experimental analysis of the benefits of long-distance migration for reproduction in arctic-nesting birds. Measurements of a controlled effect of predation risk along a 3350-kilometer north-south gradient across arctic Canada provides evidence that the risk of nest predation decreases with latitude. Thus, birds migrating further north may acquire reproductive benefits in the form of reduced predation risk. Egg predation rates measured at artificial nests along a 3000-kilometer transect decrease northwards. Quantifying the costs and benefits of migration distance is critical to understanding the evolution of long-distance migration. In migratory birds, life history theory predicts that the potential survival costs of migrating longer distances should be balanced by benefits to lifetime reproductive success, yet quantification of these reproductive benefits in a controlled manner along a large geographical gradient is challenging. We measured a controlled effect of predation risk along a 3350-kilometer south-north gradient in the Arctic and found that nest predation risk declined more than twofold along the latitudinal gradient. These results provide evidence that birds migrating farther north may acquire reproductive benefits in the form of lower nest predation risk.

Estimating the weight of polar bears from body measurements

We measured chest girth, total body length, neck circumference, and zygomatic width of polar bears (Ursus maritimus) to determine an accurate predictor of live weight. The derived equations for males and females were weight = 0.000476(chest girth)269 (r2 = 0.97) and weight = 0.000775(chest girth)259 (r2 = 0.95), respectively. Our equations were accurate for all bears >100 kg. J. WILDL. MANAGE. 53(1):188-190 Weight measurements of wild animals are useful for wildlife research and management (Talbot and McCulloch 1965). They serve as indicators of physical condition and may reflect habitat conditions and food availability. Unfortunately, measurements of weight of large animals are difficult to obtain (Cherry and Pelton 1976). Various body parameters have been examined to determine their suitability as accurate predictors of live weight (Bandy et al. 1956, McEwan and Wood 1966, Cherry and Pelton 1976). Several studies demonstrated that accurate estimates of weight can be derived from measurements of chest girth (Payne 1976, Urbston et al. 1976, Kelsall et al. 1978). In the past, weights of polar bears have been obtained by measuring chest girth with a cattle weight tape (Ketchum Mfg. Sales, Ltd., Ottawa, Ont.) (Stirling et al. 1977:54). A high correlation (r2 = 0.97) (n = 97) existed between scale and tape weights; weights of polar bears in the Churchill, Manitoba, area could be predicted to within 92% of the scale weight using a weight tape (Stirling et al. 1977). However, Stirling et al. (1977) did not measure bears >400 kg. A population study of polar bears along the On ario coast of southern Hudson Bay afforded the opportunity to investigate relationships between weights and selected body measurements. Our objective was to determine which sex-specific body measurements provided the most accurate predictor of live weight. S. Anderson, D. S. Andriashek, J. M. Broadfoot, J. F. Danyluck, C. A. Deary, J. J. Doyle, C. D. Hendry, M. J. Hunter, D. G. Joachim, C. F. Lauer, D. R. McKnight, M. A. Regis, W. H. Rohr, H. L. Smith, J. E. Thompson, and R. E. Wheeler provided field support. D. H. Belanger, J. E. Bell, J. R. Kenrick, W. R. Lannin, G. F. McAuley, C. D. MacInnes, T. J. Millard, R. P. Seguin, G. J. Smith, S. J. Toole, and J. K. Young This content downloaded from 157.55.39.116 on Sun, 18 Sep 2016 06:41:36 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 53(1):1989 POLAR BEAR WEIGHTS * Kolenosky et al. 189 provided administrative and logistic support. The Ontario Government Air Service, S. Hemphill and G. Ertel of Ranger Helicopters, and G. Lester and R. A. Laporte of Huisson Aviation provided support. B. Wilkinson typed the paper and C. D. MacInnes reviewed an early draft. This is contribution 87-10 of the Wildlife Research Section, Ontario Ministry of Natural Resources, Maple.

Goose-induced Changes in Vegetation and Land Cover between 1976 and 1997 in an Arctic Coastal Marsh

Abstract Since the 1970s, a breeding colony of lesser snow geese (Chen caerulescens caerulescens L.) at La Pérouse Bay, Manitoba, has grown 8% annually. This increase has led to significant loss of plant cover in all major salt- and freshwater coastal habitats between 1976 and 1997. A series of transects established in 1976 was resurveyed in 1997. Exposed sediment, extent and type of vegetative cover, and aquatic areas were recorded along transects using a classification of 12 a priori classes. Five regions within the colony were identified, and changes in vegetation cover differed among these and depended on unique combinations of vegetation class and year. Grubbing by geese has led to loss of graminoid plants, especially in intertidal and supratidal marshes. Exposed sediments have largely replaced previously vegetated areas since 1976. Species characteristic of disturbed sites have colonized exposed sediment with the most abundant species varying according to soil conditions. In intertidal marshes, willow cover declined in association with the development of hypersalinity after loss of the graminoid mat, but willow cover increased at the base of well-drained beach ridges and in a river delta with ample winter snow accumulation and freshwater flow in spring that protected ground vegetation. Most of the expected successional trends associated with isostatic uplift and changes in soil organic matter failed to occur because of intense goose foraging throughout the 20 years. The likelihood of sustained recovery of plant communities in the immediate coastal zone is very low, as long as goose numbers continue to increase. Indirect effects of vegetation loss (e.g., hypersalinity) and subsequent erosion of exposed sediments following grubbing will delay plant colonization and retard succession.

Influence of Arctic Terns on Survival of Artificial and Natural Semipalmated Plover Nests

Abstract Survival of Semipalmated Plover (Charadrius semipalmatus) nests was compared in areas with and without nesting Arctic Terns (Sterna paradisaea) to determine whether the protection provided to plovers by association with this colonial species is passive or aggressive. Artificial and natural nests placed ≤100 m from terns had similar rates of survival (<10% of all nests lost to predators), and benefited substantially from protection against predators through aggressive behavior of nesting terns. Natural nests had much higher survival than artificial nests when positioned >100 m from nesting terns, suggesting that the presence of incubating adult plovers reduces the probability of nest predation. Nesting in association with Arctic Terns may represent an alternate form of habitat selection by Semipalmated Plovers and suggests that plovers can employ alternate nest defense strategies when opportunities are present.

NEST SUCCESS AND HABITAT SELECTION OF THE SEMIPALMATED PLOVER ON AKIMISKI ISLAND, NUNAVUT

Abstract We studied nest site selection by Semipalmated Plovers (Charadrius semipalmatus) to compare microhabitat characteristics at nest and random sites, and to compare successful and unsuccessful nests on the northern shore of Akimiski Island, Nunavut, during 2002. Nesting birds selected sites with more pebbles and less vegetative cover than randomly available in the environment. Nest sites also had smaller percentage of bare mud than random sites. Plovers selected sites within 100 m of Arctic Terns (Sterna paradisaea) more often than expected based on the distribution of random sites in the study area. Twenty-three of 41 (56%) nests hatched successfully. None of the microhabitat features that we measured predicted nest success. All 10 nests near the colony of Arctic Terns hatched, suggesting that interspecific associations are more reliable than habitat features for predicting nest success.

Using Digital Photographs to Evaluate the Effectiveness of Plover Egg Crypsis

Abstract The focus of digital photography has moved from documentation to quantitative analysis. To illustrate the potential application of this diagnostic tool to quantify color and shape, we photographed both artificial and natural semipalmated plover (Charadrius semipalmatus) nests to determine what benefits, if any, were derived from egg crypsis (i.e., eggshell color and egg marking shape). This simple and cost-effective method provides precise and repeatable quantification of color and shape that discriminated subtle differences in egg crypsis of artificial and natural nests that were not visible to us. The advantages of digital photography and image-editing software outweigh any shortcomings, as long as standard protocols are followed for capturing and analyzing images. Used with due care, digital photography is useful in studies that need to quickly assign biological traits, such as age and sex, to individuals, and to document temporal change that may occur as a response to management or disturbance.

Molt migrant Canada geese in Northern Ontario and Western James Bay

We undertook migration monitoring surveys and analysis of long-term banding data to determine if there was a significant premolt movement of Canada geese (Branta canadensis) from restored and reintro duced populations in southern Canada and midcontinent United States into northern Ontario and western James Bay. We examined migration chronology, origins, and demographic characteristics of molt migration of Canada geese in northern Ontario and on Akimiski Island, Northwest Territories. From 1985 to 1989, a conspicuous northward migration of large Canada geese was documented throughout northern Ontario from midMay to the end of June, well after the April migration of the subarctic nesting subspecies of Canada geese (B. c. interior); most nesting interior Canada geese in the Hudson Bay and James Bay lowlands were incubating eggs at this time. Summer-banded Canada geese originating from populations in 26 states and 6 Canadian provinces were captured in coastal areas of James Bay and Hudson Bay between the borders of Quebec and Manitoba. Morphometric discrimination indicated the presence of molting giant Canada geese (B. c. maxima) Most foreign, summer-banded birds were yearlings (53%) and 2-year-olds (17%), but birds up to 15 years old were captured. Approximately 58% of 2-15-year-old females had brood patches, which indicated a nesting attempt in the year of recapture. We suggest that increasing populations of giant Canada geese and declining habitat availability on northern brood-rearing areas will result in increasing levels of competition between populations of Canada geese. Presence of molt migrants on northern breeding areas will also complicate management of some Arctic and subaretic nesting populations of Canada geese.

Can woodland caribou and the forest industry coexist: The Ontario scene

Ontario is in the process of developing a strategy to improve the likelihood of woodland caribou (Rangifer tarandus caribou) and the forest industry coexisting in the province. This strategy is described within a set of proposed Timber Management Guidelines for the Provision of Woodland Caribou Habitat. The proposed guidelines advocate managing for large blocks of suitable winter habitat across caribou range, large cutovers to regenerate caribou winter habitat and the protection of traditional calving areas and travel routes. Summer habitat will be provided by the resulting mosaic. The forest industry can provide a sustainable supply of woodland caribou habitat that was traditionally maintained by wildfire.

Predators, alternative prey and climate influence annual breeding success of a long-lived sea duck

1. Perturbations to ecosystems have the potential to directly and indirectly affect species interactions, with subsequent impacts on population dynamics and the vital rates that regulate them. 2. The few long-term studies of common eider breeding ecology indicate that reproductive success is low in most years, interrupted by occasional boom years. However, no study has explicitly examined the drivers of long-term variation in reproductive success. 3. Here, we use encounter history data collected across 41 years to examine the effects of arctic foxes (a terrestrial nest predator), local abundance and spatial distribution of lesser snow geese (an alternative prey source), and spring climate on common eider nest success. 4. Eider nest success declined over the course of the study, but was also highly variable across years. Our results supported the hypothesis that the long-term decline in eider nest success was caused by apparent competition with lesser snow geese, mediated by shared predators. This effect persisted even following a large-scale exodus of nesting geese from the eider colony. Nest success was also lowest in years of low arctic fox index, presumably driven by prey switching in years of low small mammal availability. However, increased snow goose abundance appeared to buffer this effect through prey swamping. The effect of spring climate depended on the stage of the breeding season; cold and wet and warm and dry conditions in early spring were correlated with decreased nest success, whereas warm and wet conditions in late spring increased eider nest success. 5. These results underscore the significance of both trophic interactions and climate in regulating highly variable vital rates, which likely have important consequences for population dynamics and the conservation of long-lived iteroparous species.