Alan E. Burger

Diving Birds in Cold Water: Do Archimedes and Boyle Determine Energetic Costs?

The volume of air trapped in the feathers and the body density of 36 species of water bird were determined by water displacement experiments. Body density was higher and the volume of air trapped in plumage was lower in species that were most reliant on diving for foraging. Accordingly, we predict that habitually diving species have substantially reduced energy expenditure while underwater and correspondingly higher aerobic dive limits than infrequent divers. This agrees with field observations. Following Boyles law, aerobic dive limits are predicted to increase with increasing dive depth due to a reduction in upthrust following volumetric reduction of feather-trapped air caused by hydrostatic pressure. It appears energetically more costly for diving birds to forage near the surface than at greater depths. Reduced plumage air to minimize underwater swimming costs, however, probably increases heat loss. The use of fat for insulation is not compatible with minimized flight costs. Frequent divers have higher flight costs than infrequent divers. We predict that the amount of air in the feathers and the amount of subcutaneous fat in aquatic birds are regulated in such a way as to minimize energy expenditure as a function of the temperature of the environment as well as diving and flying rhythms.

Perspectives in Ornithology Application of Tracking and Data-Logging Technology in Research and Conservation of Seabirds

The Auk A Quarterly Journal of Ornithology Vol. 125 No. 2 April 2008 The Auk 125(2):253–264, 2008  The American Ornithologists’ Union, 2008�� Printed in USA. Perspectives in Ornithology Application of Tracking and Data-logging Technology in Research and Conservation of Seabirds A lan E. B urger 1,3 and S cot t A. S haffer 2,4 Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada; and Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California 95060-5730, USA Seabirds are the most conspicuous and mobile of all pe- applications, illustrate the roles that seabirds might play in mon- lagic marine organisms. Because most species breed colonially, itoring this watery planet, and discuss the application of new researchers can study statistically large technology in the conservation and samples with relative ease. These attri- management of seabirds. We focus butes have long made seabirds valuable here on La Grangian approaches, . advances in electronic for interpreting conditions in the sur- concerned with a sequence of data technology have greatly changed rounding oceans (Furness and Cam- values at points occupied by an in- phuysen 1997, Boyd et al. 2006, Piatt et dividual organism (Schneider 1994), the way we study seabirds, al. 2007). Until recently, such studies in contrast to studies of populations were usually based on data obtained or communities made at colonies or providing unprecedented insights at breeding colonies or from vessels, from vessels or aircraft. into their locomotion, physiology, but in the past two decades, advances in electronic technology have greatly A dvancing T echnology foraging behavior, migration, changed the way we study seabirds, demographics, and exposure to providing unprecedented insights into The burgeoning market for consumer their locomotion, physiology, foraging electronics and communication (e.g., anthropogenic risks at sea.” behavior, migration, demographics, satellite and cell-phone communica- and exposure to anthropogenic risks at tion) is partly responsible for the ad- sea. In oceans that are rapidly chang- vances and miniaturization of sensors, ing as a result of human activities and global climate change, this memory storage, and batteries that are revolutionizing marine or- information from tagged birds is timely and essential for developing nithology (see reviews in Wilson et al. 2002a, Ropert-Coudert and conservation and management strategies for such wide-ranging or- Wilson 2005). We review some recent developments, focusing on ganisms. In addition, seabirds are increasingly being viewed as tools devices that tell us where birds go (satellite tracking, geolocators, for oceanography and climatology—capable of providing essential global positioning system [GPS] loggers, and depth recorders) and physical and biological information on the sea itself. what they are doing (sensors coupled with data loggers). Here, we highlight some of the exciting new techniques Tracking devices.—Before 1990, conventional VHF radio tags and data that are emerging, discuss some current and future were used to monitor colony attendance and near-colony foraging E-mail: aburger@uvic.ca Department of Biology, California State University, San Bernardino, California 92407, USA. The Auk, Vol. 125, Number 2, pages 253–264. ISSN 0004-8038, electronic ����������������  2008 by The American Ornithologists’ Union. All rights reserved. Please ISSN������������ direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www. ucpressjournals.com/reprintInfo.asp DOI: 10.1525/auk.2008.1408

Occurrence of plastic particles in seabirds from the eastern North Pacific

Abstract We found plastic particles in the stomachs of 8 of the 11 species of seabirds caught as bycatch in the pelagic waters of the eastern North Pacific (41–50°N, 131–134°W). Plastic was found in all surface-feeding birds (two stormpetrel, one albatross, one petrel and one fulmar species) and in 75% of shearwaters. Densities in some stormpetrels, shearwaters and the petrel were possibly sufficient to impede digestion, but were negligible in other birds. Plastic was also found in two diving species (puffins) but absent in three others (murre, auklet and murrelet). Of 353 anthropogenic items examined, 29% were industrial pellets and 71% were fragments of discarded products (‘user’ plastic), with user plastic making up 60% of total mass. Our study is evidence of widespread plastic pollution affecting birds in a previously unsampled sector of the North Pacific.

Differences in prey selection and behaviour during self-feeding and chick provisioning in rhinoceros auklets

We determined whether a marine diving bird, the rhinoceros auklet, Cerorhinca monocerata, used different foraging behaviour and collected different prey items for its young than when feeding itself. Foraging behaviour was determined by conducting visual scans, and prey items were sampled by collecting fish delivered to chicks and by collecting fish where auklets were self-feeding, which was verified by two other sources of information. Adult auklets ate small fish (59.1+/-0.5 mm, N=547), including juvenile Pacific sand lance, Ammodytes hexapterus, and Pacific herring, Clupea harengus, but collected larger fish to feed their chicks (95.2+/-1.3 mm, N=321), including primarily Pacific sand lance, Pacific herring, Pacific salmon species, Oncorhynchus spp., and surf smelt, Hypomesus pretiosus. In addition, auklets collected fish for themselves primarily by diving in mixed-species feeding flocks before 1600 hours, whereas they collected fish to feed their chicks by diving solitarily after 1600 hours. This suggests that auklets switched both foraging behaviour and prey selection when collecting fish for self-feeding, compared with when collecting fish for chick provisioning. Several avian studies have documented different diets of adults and chicks, but this is the first research to observe directly and document different foraging behaviour used in adult and chick provisioning. We emphasize the importance of distinguishing between self-feeding and chick provisioning in foraging and life history studies. Copyright 1999 The Association for the Study of Animal Behaviour.

Estimating the Mortality of Seabirds Following Oil Spills: Effects of Spill Volume

Abstract A statistical analysis of 45 oil spills shows a weak log-log correlation between spill volume and numbers of seabirds killed. This relationship cannot be used to predict mortality and loses its significance if one extreme case is omitted. The data show the wide variance in mortality in spills of all sizes. A loose ‘rule-of-thumb’ that is often used in poorly documented spills is that the overall mortality is ten times the actual body count. There is no justification for this notion. The mean estimate used is 4–5 times the body count, but each spill should be examined independently.

Foraging Behavior and Resource Partitioning by Diving Birds During Winter in Areas of Strong Tidal Currents

Abstract We investigated the distribution and behavior of 21 species of diving birds wintering in tidally active nearshore ocean off southern Vancouver Island, British Columbia, Canada. Using vessel surveys in one site and land-based observations at a second site, we found significant differences in the use of tidally affected water types among and within three foraging guilds (piscivores, plankton feeders and benthic invertebrate predators) and five families (Gaviidae, Podicipedidae, Phalacrocoracidae, Anatidae, Alcidae). The only abundant plankton feeder, Ancient Murrelets (Synthliboramphus antiquus), foraged more frequently than other birds in areas of deeper water (>10 m) with fast tidal flow and turbulence. Their abundance and diving activity were significantly higher at maximum tide flow than at slack tides. Piscivores used both slack water and moderate currents in a wide range of depths but, apart from alcids and Pelagic Cormorants (Phalacrocorax pelagicus), avoided areas of high current and turbulence. Pigeon Guillemots (Cepphus columba) had higher abundance at tide phases with maximum current, and within a channel with strong tidal flow they showed repetitive upstream flights interspersed with downstream diving bouts. Fish-eating mergansers and most diving ducks taking benthic invertebrates foraged in relatively shallow (<10 m) and slack water, and avoided turbulence. Six species representing all three guilds showed changes in the use of depth categories as tides changed between slack and maximum current, and four species changed their behavior in different depth categories. Although there was considerable overlap in foraging niches, the differences in distribution and behavior of guilds, families, and species of diving birds indicate a degree of resource partitioning within tidally-driven water categories during winter.

Diving Depths of Shearwaters

Abstract Maximum diving depths were measured for shearwaters breeding on Cousin Island, Seychelles. Eighty-three percent of 23 Wedge-tailed Shearwaters (Puffinus pacificus) dived, and their mean maximum depth was 14 m (SD = 23 m, range 1–66 m, N = 19). All Audubons Shearwaters (P. lherminieri) dived, and their mean maximum depth was 15 m (SD = 12 m, range 6–35 m, N = 7). These data contradict the hypothesis that tropical shearwaters should not specialize in underwater foraging. They are capable of exploiting deep prey unavailable to most other tropical seabirds. Five Puffinus species (temperate and tropical) attained allometrically scaled maximum depths comparable to those of penguins and alcids.

Dispersal and germination of seeds of Pisonia grandis , an Indo-Pacific tropical tree associated with insular seabird colonies

The distribution of the forest tree Pisonia grandis (Nyctaginaceae) coincides with seabird colonies on small tropical islands. Its seeds are enclosed in a calyx exuding extremely sticky resin which adheres strongly to feathers. Birds are obviously seed-dispersal vectors, but the multi-seeded infructescences frequently entangle birds, often fatally. On Cousin Island, Seychelles, I investigated the production, germination, survival, and tolerance to seawater of Pisonia seeds, and the occurrence of entanglement with birds. Fresh seeds had high germination success (62–87% in experimental trays), but seedling survival in Cousins forests was low (0.1% of 6020 seeds survived as seedlings after 2–8 mo). Some seeds tolerated 30 min daily immersions in seawater (8–15% germination after 14–28 d treatment), but not continuous immersion in seawater (reduced germination after 5 d and none after 12 d). Inter-island dispersal is likely via living unencumbered seabirds carrying a few seeds, but not on floating carcasses. Seeds attached to carcasses did not have improved germination or survival. Intra-island propagation is almost entirely vegetative, with negligible local seed dispersal. Pisonia plants therefore do not benefit from fatal entanglements. The extreme stickiness of the seeds evidently evolved to resist removal by seabirds and so facilitate long-distance dispersal. The mortality of some potential vectors is an unfortunate consequence, but has little impact on the large populations of tree- and ground-nesting seabirds which nest in or under these trees.

HABITAT USE AND BEHAVIOR OF THE PACIFIC SAND LANCE (AMMODYTES HEXAPTERUS) IN THE SHALLOW SUBTIDAL REGION OF SOUTHWESTERN VANCOUVER ISLAND

Abstract The Pacific Sand Lance (Ammodytes hexapterus) is an important Pacific Northwest prey species for marine predators. In our study along the West Coast Trail, southwestern Vancouver Island, British Columbia, we examined shallow subtidal habitat selection of juvenile and adult Sand Lance with respect to sediment characteristics, and also examined aggregation behavior. Analysis of presence or absence using a classification tree showed that Sand Lance avoided sites with no subtidal sediments, preferred sites with mean sediment particle sizes ≤ 1290 μm and preferred mixed sediments (sorting values >3.09 standard deviations; standard deviation of particle size used as a heterogeneity index of the substrate grain size). The regression tree analysis explained 99% of the variation in abundance based on the effects of mean particle size, particle sorting and presence or absence of sediments, but the model showed evidence of over-classification due to small sample sizes. Nevertheless, the model indicated environmental factors that are important for Sand Lance habitat use. Behavioral analysis showed that Sand Lance aggregated into larger schools to feed and these schools tended to occur in the mid-water column compared to non-feeding schools which remained closer to the seafloor. Near the beaches, 0-year (young-of-the-year) Sand Lance were found in deeper water compared to older Sand Lance (1+ -year classes). Together these data suggest that Sand Lance using the shallow subtidal show some indication of habitat use based on particle size and sorting, and aggregation differences based on behavior and age class.

Time Budgets, Energy Needs and Kleptoparasitism in Breeding Lesser Sheathbills (Chionis minor)

-Lesser Sheathbills (Chionis minor) were studied at Marion Island in the sub-Antarctic. Activity-time budgets of parents rearing chicks were converted into energy budgets and added to estimates of the food delivered to the chicks at the nest, in order to estimate the total energy costs of rearing chicks. Most of the food was obtained by stealing it from breeding penguins and it is improbable that Lesser Sheathbills could rear their chicks in the present manner without access to penguins, or possibly other colonial seabirds. Kleptoparasitism probably had little effect on the breeding success of the host Rockhopper Penguins (Eudyptes chrysocome), since a pair of sheathbills removed less than 1% of the food that the penguins brought into their territory. Investments of time, energy and risk of injury while rearing chicks were very similar for both sheathbill parents. The need to brood young chicks, owing to the harsh climate, restricted food delivery and caused chicks sometimes to starve. Kleptoparasitism, the stealing of food by one individual from another, occurs amongst many bird species but is seldom a basis for specialization (Brockmann and Barnard 1979). Sheathbills (Chionis spp.), which live in the Antarctic and sub-Antarctic, obtain a significant portion of their diets by stealing food from penguins, and occasionally from cormorants and albatrosses (Jones 1963, Burger 1979, in press a). Pairs of breeding sheathbills maintain foraging and nesting territories centered on colonies of breeding seabirds, usually penguins, and they obtain virtually all their food from these colonies. Reproduction in birds usually requires considerable investment of time and energy above the costs of normal maintenance (King 1973, Ricklefs 1974). Lesser Sheathbills (Chionis minor) apparently need to have access to a colony of penguins, or perhaps cormorants or albatrosses, in order to meet the costs of breeding (Burger 1979). In this paper I report time and energy demands of adult Lesser Sheathbills while they are rearing chicks, discuss whether breeding is theoretically possible if the birds have no access to penguins, and estimate the effects of kleptoparasitism on the breeding penguins. The division of labor between the sexes of breeding pairs is also examined. The chick-rearing period was selected as being the most demanding phase of breeding, as it is in most nidicolous bird species (Ricklefs 1974). Lesser Sheathbills’ nests are merely heaps of debris requiring little effort to make, their eggs are not large in relation to the size of the adult female and the clutch is small, averaging two or three eggs (Burger 1979). Both sexes incubate and the cost of incubation is likely to be far less than the cost of feeding chicks (King 1973, Ricklefs 1974, Drent 1975). MATERIALS AND METHODS Lesser Sheathbills are resident on four island groups in the southern Indian Ocean (Watson 1975). I studied the birds at Marion Island (46”54’ S, 37”45’ E) in the Prince Edward Islands. Observations in the austral summer of 1976/1977 concentrated on three pairs (A, B and C) which bred in adjacent colonies of Rockhopper Penguins (Eudyptes chrysocome). All six parents had been sexed (Burger 1980a) and color-banded two years before observations commenced. Pairs A and C and the female of pair B had bred successfully in the same territories for at least three seasons; the male from pair B was a three-year old bird breeding for the first time. Pairs A and B fed one chick each from hatching to fledging (about 60 days) and pair C fed three chicks for 39 days and two to fledging. Diurnal time budgets of these three pairs were determined at roughly weekly intervals from the time the chicks hatched (mid-January) until they left the nests to follow their parents (mid-March), making observations impracticable. I watched the birds from a blind from which the three nests and most of the three territories could be seen. The activities of each adult were recorded at five-minute intervals, and one of eight activities (see below) was assigned to part or the whole of each interval. The weekly observations were made on successive days to cover the periods dawn (t05:OO) to noon and noon to dark (t20:20). Adults roosted throughout the night within their territories, and the dawn-dark observations were thus sufficient to construct 24-h activity-time budgets. Bad weather severely restricted observations in the last week and where necessary in this case, the data from 385 min of observations were extrapolated to cover the 870 min of daylight. I estimated the mass of meals fed to chicks by placing ‘ chokers’ around the chicks’ necks to prevent swal-