William A. Montevecchi

Birds as indicators of change in marine prey stocks

For millenia humans have followed birds at sea to locate fish and mammals. Seabirds are highly visible wide-ranging upper trophic level consumers that can indicate marine productivity and biotic interaction. Compared with fish, marine mammals, and other animals that live primarily or exclusively underwater, seabirds are easy to survey, census and study. This chapter reviews the types, utilities and limitations of avian indicators of the condition of fish stocks and recommends research needed to improve understanding of avian trophic relationships.

Composition and energy contents of mature inshore spawning capelin (Mallotus villosus) : implications for seabird predators

Abstract 1. 1. Lipid levels of capelin are highest in late fall and lowest during the summer spawning season; protein levels are constant at 13–14% body wt throughout the year. 2. 2. Ovid females contained significantly more lipid and protein and less water and had higher energy densities than males and spent females. 3. 3. Surgically-removed egg masses made up 34.2 ± 10.3% female body wt and were very similar in composition and energy density to gravid females, differing from spent females and males in similar respects. Owing to the ovarian development of females, sexes differ in energy density only during the spawning season. 4. 4. Sexes were similar in amino acid composition. Analysis of capelin and three other seabird forage species revealed that isoleucine levels were lower than minimum avian maintenance and growth requirements. 5. 5. Implications for the foraging behaviour and food preferences of diving seabird predators (murres, puffins) are discussed.

The Relationship between Egg Size and Chick Size in the Laughing Gull and Japanese Quail

Variation in the water, lipid, and nonlipid dry matter of eggs and newly hatched chicks of the Laughing Gull and Japanese Quail was related to variation in the size of the egg. Egg contents of the two species were, on average, very similar. Yolk size varied in direct proportion to egg size, but in the quail large eggs contained disproportionately low levels of lipid and high levels of nonlipid dry matter. The composition of the newly hatched gull chick closely resembled that of the newly hatched quail. With increasing egg size, and thus chick size, water level increased and lipid level decreased in the gull chick, whereas lipid level increased in the quail chick. Among body organs, the integument of the gull exhibited a disproportionate increase with an increase in egg size, owing mostly to the accumulation of water; in the quail, the legs were the only organs to increase out of proportion to increase in body size. Disproportionate decreases in body proportion with increasing chick size appeared mostly in the head, stomach, and intestine components of both species. Variation in proportions of lipid and water in the chick related to egg size is discussed in terms of (1) ecological requirements of newly hatched chicks, (2) sibling competition within broods, and (3) stage of development of the young at hatching.

Breeding Bird Assemblages Inhabiting Riparian Buffer Strips in Newfoundland, Canada

Throughout most of the North American boreal forest, riparian buffer strips are left during clearcutting. Although this practice is considered a means to reduce adverse effects of timber harvesting on terrestrial fauna, little research has been conducted to quantify the extent to which buffer strips are used by wildlife. We compared breeding bird assemblages (grouped into 5 habitat guilds) in undisturbed shoreline habitats with those in 20-50-m-wide riparian buffer strips in balsam fir (Abies balsamea) forests on insular Newfoundland, Canada. Total avian abundance was higher along buffer strips than undisturbed shorelines because of a greater abundance of ubiquitous species and species associated with clearcut edge habitats. Abundances of forest generalist, interior forest, and riparian species were similar between buffers and controls. Riparian buffer strips provided habitat for a diverse avian assemblage and maintained many riparian and woodland species in areas of intensive clearcutting. Counts of riparian species did not increase in wider buffers, likely due to their association with habitats adjacent to water, which do not increase in proportion to strip width. Total numbers of interior forest birds, many species of which may be declining in northeastern North America, may increase in wider buffers, but these species were rare even in the widest strips sampled (40-50 m) when compared to local interior forest habitat. Furthermore, 3 of 6 species in the interior forest guild were not observed in any buffer strip. While riparian conservation is essential, separate but complementary conservation strategies clearly are required to protect riparian and interior forest species.

Seabirds at risk around offshore oil platforms in the north-west Atlantic.

Seabirds aggregate around oil drilling platforms and rigs in above average numbers due to night lighting, flaring, food and other visual cues. Bird mortality has been documented due to impact on the structure, oiling and incineration by the flare. The environmental circumstances for offshore hydrocarbon development in North-west Atlantic are unique because of the harsh climate, cold waters and because enormous seabird concentrations inhabit and move through the Grand Banks in autumn (storm-petrels, Oceanodroma spp), winter (dovekies, Alle alle, murres, Uria spp), spring and summer (shearwaters, Puffinus spp). Many species are planktivorous and attracted to artificial light sources. Most of the seabirds in the region are long-distance migrants, and hydrocarbon development in the North-west Atlantic could affect both regional and global breeding populations. Regulators need to take responsibility for these circumstances. It is essential to implement comprehensive, independent arms length monitoring of potential avian impacts of offshore hydrocarbon platforms in the North-west Atlantic. This should include quantifying and determining the nature, timing and extent of bird mortality caused by these structures. Based on existing evidence of potential impacts of offshore hydrocarbon platforms on seabirds, it is difficult to understand why this has not been, and is not being, systematically implemented.

Nest site selection and its survival value among laughing gulls

Summary1.The nesting strategy as determined by nonrandom variation in environmental features at laughing gull (Larus atricilla) nests in a salt marsh was studied (Fig. 3). Gulls tended to nest on mats in tall grass that grows on low ground (just above high tides) near water (Figs. 4–7). Grass height was inversely related to ground elevation and distance to water (Fig. 8). Throughout the season, gulls selected nest sites in grass about 35 cm in height; due to continued grass growth, early breeders had taller grass around nests (Fig. 9). Pairs in the colony center nested earlier and in taller grass than pairs in a peripheral area.2.Mats apparently stabilize nests during flooding, and by settling on mats gulls may conserve energy in the collection of nest material. Tall grass around nests afforded chicks protection from predators and weather, and held floating nests in place during flooding.3.Gulls spend about 4 weeks (two spring tidal cycles) on the nesting grounds before egg laying. During this time they perform virtually no nest building and probably gain important information about nest site suitability.4.Tidal flooding, the greatest threat to reproductive success—destroying 70–100% of the nests in the colony — occurred on average once every 2 years over 10 years. Floods occurred during spring tides accompanied by sustained NE winds.5.Following a flood that destroyed 70% of the nests in the colony, it was shown that a significantly greater proportion of successful pairs nested on mats and in significantly taller grass than unsuccessful pairs. Grass height, especially that on the SW side of the nest, was the most important predictor of success during flooding.6.More pairs in the central area were successful than those in the peripheral one: the result of nesting in taller grass and the greater protection of the central area from tides and winds. Though not differing among successful and unsuccessful nesters, females in the peripheral area laid smaller eggs and clutches, and laid later than females in the central area (over 3 years), suggesting that females in the peripheral area were on average younger than females in the central area. It was speculated that, on average, younger pairs will experience during flooding lower reproductive success as a result of nesting inexperience and nesting in suboptimal habitat. The smaller reproductive investments of younger pairs in eggs and clutches can be interpreted as an adaptation to conserve energy during a period of the life cycle when new behavioral adjustments and nesting areas are being explored.

Stable isotopic determinations of trophic relationships of great auks

SummaryStable isotopic ratios of animal tissues are related to those of their foods and can be used in palaeoecological reconstructions, including those of extinct animals. Nitrogen isotopic analyses of marine organisms from coastal Newfoundland and Georges Bank were used to construct a model predicting collagen δ15N values for seabirds feeding at various trophic levels (TL). This model was tested by measuring bone collagen δ15N values of extant alcids from the northwest Atlantic and high Arctic. Isotopic analysis of bone collagen of the extinct great auk (Pinguinus impennis), the last flightless seabird in the northern hemisphere, indicate that this species occupied a trophic continuum from TL3 (crustacean diets) to TL5 (diets of piscivorous fish). We suggest that (a) great auk chicks and juveniles occupied lower trophic levels and probably consumed euphausiids, and (b) great auks fed offspring via regurgitation, as do dovekies (Alle alle), the only extant fully planktivorous alcid in the Atlantic, and unrelated penguins of the southern hemisphere.

Genetic structure of thick-billed murre (Uria lomvia) populations examined using direct sequence analysis of amplified DNA

Recent research has revealed that the extent of genetic differentiation of animal populations varies greatly (reviewed by Avise et al., 1987), and appears to be negatively correlated with dispersal capability (Ball et al., 1988). Most birds are highly mobile, and correspondingly most avian populations have little if any genetic structuring (e.g., see review by Evans, 1987; also Tegelstrom, 1987; Ball et al., 1988). However, many avian species exhibit strong natal philopatry, and genetic differentiation of demes within some species is substantial, despite high dispersal capabilities (e.g., Canada geese, Branta canadensis; Van Wagner and Baker, 1986; Shields and Wilson, 1987; black brant, B. bernicla; Shields, 1990; fairy prions, Pachyptila turtur; Ovenden et al., 1991). Most previous population genetics studies of birds involved protein electrophoresis, which may not be sufficiently sensitive to detect genetic structuring in many cases. Because mitochondrial DNA (mtDNA) is haploid and maternally inherited, its effective population size is 1/4 that of nuclear genes. MtDNA is therefore affected by founder effects, bottlenecks, and genetic isolation more than are nuclear genes (Birky et al., 1983; Wilson et al., 1985). MtDNA also evolves more quickly than do nuclear-encoded proteins (Brown et al., 1979; Wilson et al., 1985), and although mtDNA analyses are based on only one locus, restriction endonuclease studies of mtDNA have proven more sensitive than protein electrophoresis in detecting genetic structure in many animal species, particularly birds (e.g., Ovenden et al., 1987; Shields and Wilson, 1987; Shields, 1990). Restriction analyses however miss many mutations, such as multiple substitutions within single

Nest Site Selection in the Terrapin Malaclemys terrapin

Northern diamondback terrapins nesting in sand dunes on Little Beach Island, Brigantine, New Jersey were studied during June and July 1973 to determine the factors affecting the timing of egg laying and the selection of nest sites. One to three censuses were taken daily over a transect 800 m long and 18 m wide at various times of the day. Turtles were found laying from 10 June through 23 July, between the daylight hours of 0700 h to 1900 h. There was no correlation between the time of day and the number of turtles on the nesting area. There was, however, a high positive correlation between the number of turtles in the census area and the height of the tide. Beaching at high tide decreases the time the turtle is exposed to predation, thermal stress and desiccation, decreases the distance the turtle must walk to reach the nesting area, and increases the turtles chance of nesting above high tide. The nesting area of diamondback terrapins is an old, vegetated dune near a cove and behind the barrier beach. Within the study area the turtles preferred to nest in the high dune area compared to available low dune and flat sand areas. However, specific nest sites were on low slopes in areas of low vegetation cover. Nesting in a vegetated area provides a stable substrate, while placing the nest away from the vegetation reduces the number of roots encountered while digging. We suggest that the choice of high dune areas functions to promote laying well above the high tide. Nesting on low slopes within the high dune area minimizes the problems of digging on a steep incline and reduces erosion around

Changes in Canadian seabird populations and ecology since 1970 in relation to changes in oceanography and food webs.

Systematic monitoring of seabird populations in Canada has been ongoing since the 1920s and the monitoring of diets and other biological indicators of ecosystem change started in the 1970s. Long-te...