Pelagic Cormorants Research Articles

Survival costs of reproduction are independent of energy costs in a seabird, the pelagic cormorant.

Life-history theory predicts that investment in reproduction should decrease survival (the 'cost of reproduction'). It is often assumed that energy allocation drives such trade-offs, with limited energy available for both reproduction and survival. However, the underlying mechanisms remain poorly understood, maybe because survival costs of reproduction are only apparent when resources are limited. Here, we took advantage of a natural experiment created by fluctuating environmental conditions to compare energy expenditure of a seabird, the pelagic cormorant (Phalacrocorax pelagicus), between contrasting population-scale scenarios of survival costs of reproduction. We used multi-state capture-recapture modelling across 16 years to identify which breeding seasons induced high survival costs (survival ratebreeders < survival ratenon/failed breeders) and we concomitantly estimated energy expenditure of chick-rearing males using time-energy budget models across 4 years. Daily energy expenditure (DEE) of chick-rearing pelagic cormorants varied significantly among years. However, survival costs of reproduction were observed in only 1 year, and contrary to our expectations, variation in DEE was not associated with population-level survival costs. Similarly, at the individual level, DEE in 1 year did not predict the probability of being observed again at the colony in following years (apparent survival). Finally, DEE was independent of brood size and brood age, but older individuals tended to expend less energy than younger ones. Given the lack of an apparent energetic 'cost of reproduction', lower DEE in older birds could be due to improved efficiency rather than avoidance of costs in old birds. Although future studies should account for potential sex-specific energetic constraints by including data on female energy expenditure, we conclude that a direct link between the rate of energy expenditure during breeding and subsequent survival is unlikely in this system.

Amino acid-specific isotopes reveal changing five-dimensional niche segregation in Pacific seabirds over 50 years

Hutchison’s niche theory suggests that coexisting competing species occupy non-overlapping hypervolumes, which are theoretical spaces encompassing more than three dimensions, within an n-dimensional space. The analysis of multiple stable isotopes can be used to test these ideas where each isotope can be considered a dimension of niche space. These hypervolumes may change over time in response to variation in behaviour or habitat, within or among species, consequently changing the niche space itself. Here, we use isotopic values of carbon and nitrogen of ten amino acids, as well as sulphur isotopic values, to produce multi-isotope models to examine niche segregation among an assemblage of five coexisting seabird species (ancient murrelet Synthliboramphus antiquus, double-crested cormorant Phalacrocorax auritus, Leach’s storm-petrel Oceanodrama leucorhoa, rhinoceros auklet Cerorhinca monocerata, pelagic cormorant Phalacrocorax pelagicus) that inhabit coastal British Columbia. When only one or two isotope dimensions were considered, the five species overlapped considerably, but segregation increased in more dimensions, but often in complex ways. Thus, each of the five species occupied their own isotopic hypervolume (niche), but that became apparent only when factoring the increased information from sulphur and amino acid specific isotope values, rather than just relying on proxies of δ15N and δ13C alone. For cormorants, there was reduction of niche size for both species consistent with a decline in their dominant prey, Pacific herring Clupea pallasii, from 1970 to 2006. Consistent with niche theory, cormorant species showed segregation across time, with the double-crested demonstrating a marked change in diet in response to prey shifts in a higher dimensional space. In brief, incorporating multiple isotopes (sulfur, PC1 of δ15N [baselines], PC2 of δ15N [trophic position], PC1 and PC2 of δ13C) metrics allowed us to infer changes and differences in food web topology that were not apparent from classic carbon–nitrogen biplots.

State of the California Current Ecosystem report in 2022: a tale of two La Niñas

2022 marked the third consecutive La Niña and extended the longest consecutive stretch of negative Oceanic Niño Index since 1998-2001. While physical and biological conditions in winter and spring largely adhered to prior La Niña conditions, summer and fall were very different. Similar to past La Niña events, in winter and spring coastal upwelling was either average or above average, temperature average or below average, salinity generally above average. In summer and fall, however, upwelling and temperature were generally average or slightly below average, salinity was close to average and chlorophyll a was close to average. Again, as during prior La Niña events, biomass of northern/southern copepods was above/below average off Oregon in winter, and body size of North Pacific krill in northern California was above average in winter. By contrast, later in the year the abundance of northern krill dropped off Oregon while southern copepods increased and body sizes of North Pacific krill fell in northern California. Off Oregon and Washington abundances of market squid and Pacific pompano (indicators of warm, non-typical La Niña conditions) were high. In the 20th century, Northern anchovy recruitment tended to be high during cold conditions, but despite mostly warm conditions from 2015-2021 anchovy populations boomed and remained high in 2022. Resident seabird reproductive success, which tended in the past to increase during productive La Niña conditions was highly variable throughout the system as common murre and pelagic cormorant, experienced complete reproductive failure at Yaquina Head, Oregon while Brandt’s cormorant reproduction was average. At three sampling locations off central California, however, common murre reproduction was close to or above average while both pelagic and Brandt’s cormorant were above average. California sealion reproduction has been above average each year since 2016, and pup weight was also above average in 2022, likely in response not to La Niña or El Niño but continuous high abundance of anchovy. The highly variable and often unpredictable physical and biological conditions in 2022 highlight a growing recognition of disconnects between basin-scale indices and local conditions in the CCE. “July-December 2022 is the biggest outlier from individual “strong” La Niña (events) ever going back to the 50s.” – Nate Mantua

Perfluoroalkyl Substances in Seabird Eggs from Canada's Pacific Coast: Temporal Trends (1973-2019) and Interspecific Patterns.

Whether perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) are responding to legislative restrictions and showing decreasing trends in top marine predators that range across the eastern North Pacific Ocean is unclear. Here, we examined longer-term temporal trends (1973-2019) of 4 PFSAs and 13 PFCAs, as well stable isotopes of δ13C and δ15N, in the eggs of 4 seabird species sampled along a nearshore-offshore gradient; double-crested cormorants (Nannopterum auritum), pelagic cormorants (Urile pelagicus), rhinoceros auklets (Cerorhinca monocerata), and Leach's storm-petrels (Hydrobates leucorhous) from the Pacific coast of British Columbia, Canada. PFOS was the most abundant PFSA (79-94%) detected in all eggs regardless of colony and year, with the highest concentrations, on average, measured in auklet eggs (mean = 58 ng g-1, range = 11-286 ng g-1 ww). Perfluoroundecanoic acid (PFUdA) and perfluorotridecanoic acid (PFTriDA) were the dominant long-chain PFCAs (≥30% combined). The majority of PFSAs (including PFOS) are statistically declining (p < 0.001) in the eggs of all 4 species with PFOS half-lives ranging from 2.6 to 7.8 years. Concentrations of long-chain PFCAs exhibited a trajectory comprised of linear increases and second-order declines, suggesting that the rate of uptake of PFCAs is slowing or leveling off. These trends are consistent with the voluntarily ceased production of PFSAs by 3M circa 2000-2003 and are among the first from the northeast Pacific to indicate a positive response to several regulations and restrictions on PFCAs from facility emissions and product content.

Surveying cliff-nesting seabirds with unoccupied aircraft systems in the Gulf of Alaska

Drones, or unoccupied aircraft systems (UAS), can transform the way scientific information on wildlife populations is collected. UAS surveys produce accurate estimates of ground-nesting seabirds and a variety of waterbirds, but few studies have examined the trade-offs of this methodology for counting cliff-nesting seabirds. In this study, we examined how different UAS survey parameters might influence seabird counts for population monitoring and assessed behavioral responses to aerial surveys for three sub-Arctic seabird taxa in the Gulf of Alaska: common murres (Uria aalge), black-legged kittiwakes (Rissa tridactyla), and pelagic and double-crested cormorants (Phalacrocorax pelagicus and Phalacrocorax auritus). We flew two commercially available models of UAS in planned approaches at different speeds and distances from colonies during incubation and chick-rearing periods. We compared counts from UAS-derived images with those from vessel-based photography and assessed video recordings of individual birds’ behaviors for evidence of disturbance during UAS operations and control phases. Count estimates from UAS images were similar to or higher than those from conventional vessel-based images, and UAS were particularly effective at photographing birds at sites with high cliff walls or complex topography. We observed no significant behavioral responses to the UAS by murres or cormorants, but we did observe flushing by black-legged kittiwakes during UAS flights; most of these birds were not incubating or brooding. At both the colony and individual level, we observed slightly greater responses to the smaller UAS platform and closer approaches. These results inform both species specific and general best practices for research and recreational usage of UAS near cliff-nesting seabird colonies.

Морские птицы острова Тайночин (залив Шелихова, Охотское море)

The north of the Sea of Okhotsk is one of the least studied areas in Russia's Far East. Tainochin Island (61°48'35"N 159°19'35"E) in the north of Shelikhov Bay, despite its small size, supports a very large seabird colony of seabirds. The first and the only survey of seabird colonies on the island was held back in 1994. In 2017 more than 1000 digital images of colonies were made during a single- day survey (7.06.2017). We used these digital photographs to count seabirds on the island in order to compare the current species composition and numbers with historical data. In 2017, the numerous species were the Common Murre and the Thick-billed Murre (more than 45.5 thousand individuals, two species combined), the Black-legged Kittiwake (more than 13.5 thousand individuals), and the Slaty-backed Gull (more than 1.5 thousand individuals). Common species included the Tufted Puffin (324 individuals) and the Pelagic Cormorant (280 individuals). Rare species embraced the Spectacled Guillemot (13 individuals) and the Horned Puffin (7 individuals). The Parakeet Auklet, observed in small numbers in 1994, was not recorded in 2017. The numbers of the Tufted Puffin may be underestimated, assumingly making about 1.5-2 thousand individuals. The total number of breeding seabirds (more than 61 thousand individuals) might have been stable for decades, despite the relative accessibility of the island to humans. The Common Murre population has slightly declined (from 47K to 44K individuals), presumably due to regular egg harvesting. Simultaneously, there has been an increase in the number of Slaty-backed Gulls and Pelagic Cormorants.

Состояние колоний морских птиц полуострова Старицкого (Тауйская губа, Охотское море)

Comparison of the 2019 census results with those obtained earlier permits to evaluate changes in the number and distribution of nesting seabird colonies оn the Staritsky Peninsula over the past 10 years. The Staritsky Peninsula coasts and the Gertner and Veselaya bay islands are located in close proximity to the city of Magadan, and therefore are subject to maximum anthropogenic pressure. The total number of breeding seabirds (including the urban population of the Slaty-backed Gull in the city of Magadan) increased from 36 thousand individuals in 2009 to 57.6 thousand individuals in 2019. Simultaneously, the proportion of main species changed in the largest colonies around the city - on the Tri Brata Islands and Cape Ostrovnoy. A very large colony (3,230 birds) of the Pelagic Cormorants near the mouth of the Dukcha River, which appeared in the last 20 years, now became the largest in the Tauy Bay. The colony formation and growth was promoted by the urban wastewaters discharged into the Gertner Bay.

Colonial Nesting Birds of Peter the Great Bay, Sea of Japan (Pelecaniformes, Ciconiiformes)

This study reports recent data on the distribution and breeding abundance of seven species of colonial birds on the coast of Peter the Great Bay, Sea of Japan. Over the past 30 years, three species of cormorants (great, Japanese, and pelagic cormorants), as well as the black-faced spoonbill, have significantly increased their numbers. The number of breeding pairs of gray heron and Chinese egret decreased, while the numbers of the little egret did not change.

Long-term declines in common breeding seabirds in Japan

SummaryGlobal seabird populations are in decline, with nearly half of all seabird species currently in an extinction crisis. Understanding long-term seabird population trends is an essential first step to inform conservation actions. In this study, we assembled historical breeding records of seabirds throughout the Japanese archipelago and quantified the long-term population trends of 10 major breeding seabird species using a hierarchical Bayesian state-space model. The model revealed that six species had increasing or no detectable trends (Short-tailed Albatross Phoebastria albatrus, Leach’s Storm Petrel Oceanodroma leucorhoa, Pelagic Cormorant Phalacrocorax pelagicus, Japanese Cormorant Phalacrocorax capillatus, Spectacled Guillemot Cepphus carbo, and Rhinoceros Auklet Cerorhinca monocerata). However, decreasing trends were found not only in nationally threatened species (Common Murre Uria aalge, and Tufted Puffin Fratercula cirrhata) but also common species that are often described as abundant (Black-tailed Gull Larus crassirostris and Slaty-backed Gull Larus schistisagus). These declining species have declined to 3–35% of baseline levels over the past 30 years. This study provides the first evidence of long-term declines in common and widespread seabirds in Japan.

Seabirds Breeding in Open Nests on the Yamskie Islands (Sea of Okhotsk): Numbers and Distribution

Abstract—The Yamskie Islands archipelago is regarded as a key marine bird area of global importance and since 1982 has been part of the Magadanskii Nature Reserve. The first survey of seabird numbers was conducted there in 1974 by A.G. Velizhanin. So far, his data for the Atykan, Baran, and Khatemalyu islands remain the only available information. On August 3, 2016, full photo surveys of the colonies of seabirds on these islands were carried out. The species list of all three islands includes six seabird species breeding in open nests: the Northern Fulmar, Pelagic Cormorant, Slaty-backed Gull, Black-legged Kittiwake, and Common and Thick-billed murres. Breeding of six auklet species in hidden nests and screes was confirmed: the Spectacled Guillemot, Tufted and Horned Puffins, Parakeet Auklet, and Crested and Least Auklets. The total numbers of seabirds nesting on Atykan, Baran, and Khatemalyu islands amount to more than 305 900, 103 500, and 102 000 individuals, respectively. In comparison with the previous counts, the following numerical trends have been noted. Considerable growth in the abundance of the Northern Fulmar on Atykan and Baran islands, the expansion of this species to Khatemalyu Island, and its presently high numbers on this island have been observed. The nesting population of the Black-legged Kittiwake has grown on all islands by more than twice. The abundance of the Pelagic Cormorant, which is the rarest species on the archipelago, has grown on Baran and Khatemalyu islands, which are both located closer to the mainland, with the first nests having already appeared on the most remote Atykan Island. A growing abundance of murres is noted only for Atykan Island. The stable numbers of murres on the small Baran and Khatemalyu islands possibly reflects the maximum saturation of nesting rocks accessible to murres.

Breeding Population Sizes, Distributions, and Trends of Pelagic, Double-Crested, and Brandt's Cormorants in the Strait of Georgia, British Columbia, 1955–2015

After initial colonization of the Strait of Georgia in the late 19th and early 20th centuries, nesting populations and number of colonies of Pelagic Cormorant (Phalacrocorax pelagicus) and Double-crested Cormorant (P. auritus) increased in abundance until 1987, but subsequently both species declined by 2000. To update population status, we conducted surveys of 45 Pelagic Cormorant and 24 Double-crested Cormorant nesting colonies in 2014, and supplemented this survey with recent and historic counts conducted from 1955 to 2015. We modeled changes in population size over 6 decades to measure long-term population changes, and found strong non-linear trends that varied widely among colonies. Using years when all known colonies in the Strait of Georgia were surveyed, we documented that the Pelagic Cormorant population increased from 961 to 2234 nests in 1959–1974, remained fairly stable (approximately 2250–2450 nests) from 1974 to 1987, decreased after 1987 to approximately 1100 nests in 2000, and then rose slightly to approximately 1400 nests in 2014. The Double-crested Cormorant population increased from approximately 250 nests from 1959–1960, to approximately 1900 nests in 1987, before decreasing to approximately 600 nests in 2000, and remaining at this level through 2014. Many smaller colonies of both cormorant species no longer exist, and the majority of Pelagic and Double-crested Cormorants currently nest on Mandarte Island, Mitlenatch Island, and 3 bridge locations (Second Narrows, and Burrard & Granville) in Vancouver. The main factors apparently causing decline after 1987 are increased predation and disturbance by Bald Eagles (Haliaeetus leucocephalus), a potential reduction in availability of forage-fish prey, and human disturbance. Remaining large colonies offer some protection from eagle impacts (cliff habitats or man-made structures) or alternate avian prey for Bald Eagles, such as Glaucous-winged Gulls (Larus glaucescens) at Mandarte and Mitlenatch islands. In 2013–2015, small numbers of Brandt's Cormorants (P. penicillatus) nested at Mandarte Island. Continued monitoring is needed to track changes in populations and nesting locations and to inform management of cormorants in the Strait of Georgia.

Historical Breeding By Pelagic, Double-Crested, and Brandt's Cormorants In the Salish Sea, 1891–1955

Breeding within the Salish Sea by Pelagic Cormorant (Phalacrocorax pelagicus), Double-crested Cormorant (P. auritus) and Brandt's Cormorant (P. penicillatus) was summarized from published and unpublished sources for the 1891–1955 period. None of the 3 cormorant species were recorded breeding in the Salish Sea between 1792 and 1891 although sporadic breeding may have been missed. Pelagic Cormorants were first reported breeding at Mandarte Island, British Columbia, in 1891 and afterwards bred there regularly; by 1955, 22 colonies had formed in the central and northern Salish Sea, including the San Juan Islands (n = 9), Gulf Islands (n = 5), inner Strait of Juan de Fuca (n = 4), and northern Strait of Georgia (n = 4). Before regular breeding by Double-crested Cormorants began at Mandarte Island (1927) and Ballingall Islets (1934), they apparently bred sporadically at St. John's Point (Hornby Island) in the northern Salish Sea (1896) and Mandarte Island (1900). By 1955, 8 colonies had formed in the central and northern Salish Sea, including the San Juan Islands (n = 3), Gulf Islands (n = 3) and northern Strait of Georgia (n = 2). Brandt's Cormorants only bred sporadically in the San Juan Islands at Flattop Island (1928), Matia Island (1940) and Lopez Island (<1953). Evidence of breeding in the central Salish Sea by all 3 cormorant species suggested resettlement of individuals from colonies on the outer west coast of Washington through the Strait of Juan de Fuca. Subsequent expansion by Pelagic and Double-crested cormorants in the central and northern Salish Sea suggested local growth after colonization, although impacts from human disturbance and predators affected certain colonies. Reduced harvesting by the shrinking population of indigenous peoples at cormorant colonies on the outer coast of Washington likely prompted colonization of the Salish Sea.

EFECTOS DE LAS MAREAS Y DE LOS PERÍODOS INTRA ESTACIONALES EN EL COMPORTAMIENTO DE LOS CORMORANES PELÁGICOS (Phalacrocorax pelagicus Pallas, 1811) DURANTE EL BUCEO EN CATTLE POINT, SAN JUAN ISLAND, WASHINGTON, U.S.A

The influence of time of day, tidal depth, current and inside-season change on the diving behavior of pelagic cormorants, as well as the relationships between diving time and the preceding and the subsequent surface time were examined at Cattle Point, San Juan Island. Diving behavior was recorded using focal animal sampling. Dives and surfaces were timed to the nearest second. Correlations between dive time and the other variables were analyzed using regression analysis and t-test of significance. On a daily basis, dive times varied with time of day, tidal depth and current direction. Dive times were longer later in the day, showing a trend to be longer when height of the tide was higher and during ebb tides. However, dive times remained variable throughout the course of the season. No inside-season related variation on diving times was found, probably due to changes in prey availability. Mean dives and recovery times were 31.2 sec and 19.1 sec respectively showing that dive times were longer than surface times. Even so, positive relationships were found between dive time and the preceding surface time and between dive time and the subsequent surface time suggesting that cormorants utilize both anticipatory and reactive breathing according to the foraging environment.

Counting calories in cormorants: dynamic body acceleration predicts daily energy expenditure measured in pelagic cormorants.

The integral of the dynamic component of acceleration over time has been proposed as a measure of energy expenditure in wild animals. We tested that idea by attaching accelerometers to the tails of free-ranging pelagic cormorants (Phalacrocorax pelagicus) and simultaneously estimating energy expenditure using doubly labelled water. Two different formulations of dynamic body acceleration, [vectorial and overall DBA (VeDBA and ODBA)], correlated with mass-specific energy expenditure (both R(2)=0.91). VeDBA models combining and separately parameterizing flying, diving, activity on land and surface swimming were consistently considered more parsimonious than time budget models and showed less variability in model fit. Additionally, we observed evidence for the presence of hypometabolic processes (i.e. reduced heart rate and body temperature; shunting of blood away from non-essential organs) that suppressed metabolism in cormorants while diving, which was the most metabolically important activity. We concluded that a combination of VeDBA and physiological processes accurately measured energy expenditure for cormorants.

Decline of the Pelagic Cormorant in Western Queen Charlotte Strait, British Columbia, 1975–2014

Abstract In July 2014, we conducted nest counts at 7 of 8 known breeding colonies of Pelagic Cormorants (Phalacrocorax pelagicus) in western Queen Charlotte Strait, British Columbia, to assess the current status of this population. Four nests were found on Dugout Rocks, the only known colony still used; 1 nest was found at Pine Island, a 9th (newly recorded) breeding location in the region. Total numbers of nests in this region declined 97% from 197 to 231 nests in 1975–1976, to 60 nests in 1982–1988, to 5 nests in 2014. Limited evidence suggests that Bald Eagle (Haliaeetus leucocephalus) disturbance and predation may be the main reason for this major decline in the cormorant breeding population. Historical population size of Pelagic Cormorants prior to the 1960s also may have been quite low, with breeding 1st recorded in this region in 1968, although little prior survey effort occurred. Population growth probably occurred in the 1960s and early 1970s to reach the population size noted during the 1st comp...

COLONIAL DEFENSE BEHAVIOR IN DOUBLE-CRESTED AND PELAGIC CORMORANTS

COLONIAL DEFENSE BER A VIOR IN DOUBLE-CRESTED AND PELAGIC CORMORANTS DOUGLAS SIEGEL-CAUSEY 1 AND GEORGE L. H UNT, JR. Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92717 USA ABsTRACT.- We eicamine the predictions, based upon the hypotheses of Coulson (1968), Ham- ilton (1971), and Vine (1971), that (I) spedes whose colonies are accessible to predators should form tighter groupings and have fewer isolated nests than those with reduced accessibility to predators, (2) nests at the center should be less subject to predation than those at the edge of a colony, (3) nests both in the center and with reduced accessibility should have the lowest predation pressure of all nests, and (4) individuals that nest in accessible locations should have more vigorous and more sustained antipredator behaviors than those individuals unlikely to come frequently in contact with predators. To test these predictions, we compare intrusions by two predators, the Northwestern Crow (Corvus cauri11us) and the Glaucous-winged Gull (Larus glaucescens), at isolated and grouped nests of the cliff-face nesting Pelagic Cormorant (Phalacrocorax pelagicus) and cliff-top nesting Double-crested Cormorant (P. auritus) on Mandarte Island, British Colum- bia. Both crows and gulls preferred to visit the edge nests of both species, especially those on level ground. The steeper and more central the nest location, the less likely was visitation. Gulls were restricted by topography from entering the Pelagic colony, while crows were able to land in either colony. Predator success was high only in flat, accessible areas. Both cormorant species depend upon the habitat to deter predator access: the Double-crested Cormorant utilizes a defense regime of energetic and aggressive behaviors; the Pelagic Cormorant uses a much less effective defense and depends much more on the habitat as a necessary part of nest defense. Received 11 July 1980, accepted 21Ja11uary1981. WE here examine aspects of colonial nesting in relation to their effectiveness as protection against intruding predators. Nesting phenology (Nelson 1966, 1970), lo- cation within the colony (Coulson 1968), and the topography of the colony (Nelson 1967, Nettleship 1972) have been identified as actual or potential factors in deter- mining the likelihood that a particular nest will be subject to predation. H amilton (1971) hypothesized that the clumping of prey provides a significant defense against predation, and Coulson (1968) and Vine (1971) hypothesized that individuals at the center of a group will be at a lesser riisk than those at the edge. To test the hypotheses concerning the importance of nest location in predator avoidance, we examine the interactions between two species of prey, the Double- crested Cormorant (DCC: Phalacrocorax auritus) and the Pelagic Cormorant (PC: P. pelagicus), and two species of predators, the Northwestern Crow (Con.ms caur- inus) and the Glaucous-winged Gull (Larus glaucescens), at cormorant nesting col- onies on Mandarte Island, British Columbia, Canada. In this study, we had the opportu nity to compare the activity and effect of a highly maneuverable predator (the Northwestern Crow) and a relatively clumsy predator (the Glaucous-winged Gull) as they attempted to steal eggs and small chicks from cormorant nests. Because the two species of cormorant prefer different nesting habitats and consequently have different structures for their colonies, we were able to compare the antipredator behaviors and their effectiveness for cormorants nesting on cliffs (Pelagic Cormorant) and for those nesting on level areas (Double-crested Cormorant) and for tightly clumped as well as loosely grouped nests. ' Present address: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721 USA. The Auk 98: 522-531. July 1981

High flight costs, but low dive costs, in auks support the biomechanical hypothesis for flightlessness in penguins.

Flight is a key adaptive trait. Despite its advantages, flight has been lost in several groups of birds, notably among seabirds, where flightlessness has evolved independently in at least five lineages. One hypothesis for the loss of flight among seabirds is that animals moving between different media face tradeoffs between maximizing function in one medium relative to the other. In particular, biomechanical models of energy costs during flying and diving suggest that a wing designed for optimal diving performance should lead to enormous energy costs when flying in air. Costs of flying and diving have been measured in free-living animals that use their wings to fly or to propel their dives, but not both. Animals that both fly and dive might approach the functional boundary between flight and nonflight. We show that flight costs for thick-billed murres (Uria lomvia), which are wing-propelled divers, and pelagic cormorants (Phalacrocorax pelagicus) (foot-propelled divers), are the highest recorded for vertebrates. Dive costs are high for cormorants and low for murres, but the latter are still higher than for flightless wing-propelled diving birds (penguins). For murres, flight costs were higher than predicted from biomechanical modeling, and the oxygen consumption rate during dives decreased with depth at a faster rate than estimated biomechanical costs. These results strongly support the hypothesis that function constrains form in diving birds, and that optimizing wing shape and form for wing-propelled diving leads to such high flight costs that flying ceases to be an option in larger wing-propelled diving seabirds, including penguins.

Set-Back Distances to Protect Nesting and Roosting Seabirds Off Vancouver Island from Boat Disturbance

Abstract. Recreational boat traffic is increasing worldwide and there is a need for scientifically based regulations that sustain both seabirds and wildlife viewing. The effects of boat disturbance to seabirds off Vancouver Island, Canada were quantified by testing distances that roosting or nesting birds showed an agitation response to an approaching motorboat or a kayak. The effects of species sensitivity, vessel type, habituation and season on agitation distance were examined. At 40 m from approaching boats, nesting Double-crested (Phalacrocorax auritus) and Pelagic (P. pelagicus) cormorants, Black Oystercatchers (Haematopus bachmani), Glaucous-winged Gulls (Larus glaucescens), and Pigeon Guillemots (Cepphus columba) had less than 6% probability of being agitated with either a kayak or motorboat, while at 50 m there was less than 2% probability of agitation. Roosting birds had larger response distances than nesting birds. Roosting Harlequin Ducks (Histrionicus histrionicus) were particularly sensitive ...

Responses of Pelagic Cormorants (Phalacrocorax pelagicus) to Marine Traffic and Bald Eagles (Haliaeetus leucocephalus) in Barkley Sound, British Columbia

Key words: Bald Eagle, Barkley Sound,British Columbia, decline, disturbance, Haliaee-tus leucocephalus, marine traffic, Pelagic Cormo-rant, Phalacrocorax pelagicus, set-backIn Barkley Sound, British Columbia, PelagicCormorants (Phalacrocorax pelagicus), while for-merly abundant (Vermeer and Rankin 1984),have suffered massive declines of up to 85%since 1969 (Carter and others 2007). Thisdecline is thought to be due in part todisturbance by humans and Bald Eagles (Ha-liaeetus leucocephalus) (Chatwin and others 2002;Carter and others 2007). In an attempt toinvestigate the causes of this decline, weundertook a brief study of Pelagic Cormorantswithin Barkley Sound during the nestingperiod in the summer of 2011.Nesting birds are vulnerable to disturbancefrom predators and human interference (Burgerand Gochfeld 1994; del Viejo and others 2004).Disturbance during the nesting period cancause increased stress and behavioral responses,such as flight behavior or nest avoidance, whichmay eventually lead to increased nest preda-tion, thermal shock in eggs, decline in thebreeding success of individuals, and a decreasein the density of breeding pairs (Le Corre andothers 2009). Seabirds are especially vulnerable,as many are relatively long-lived and may bemore inclined to abandon a given breedingattempt and defer breeding until future oppor-tunities (Stearns 1976).Motorized boats have been shown to disturbseabirds in more than 1 study (Burger 1998;Rodgers and Schwikert 2002), and it has been

Migration and wintering sites of Pelagic Cormorants determined by satellite telemetry

Factors affecting winter survival may be key determinants of status and population trends of seabirds, but connections between breeding sites and wintering areas of most populations are poorly known. Pelagic Cormorants (Phalacrocorax pelagicus; N= 6) surgically implanted with satellite transmitters migrated from a breeding colony on Middleton Island, northern Gulf of Alaska, to wintering sites in southeast Alaska and northern British Columbia. Winter locations averaged 920 km (range = 600–1190 km) from the breeding site. Migration flights in fall and spring lasted ≤5 d in four instances. After reaching wintering areas, cormorants settled in narrowly circumscribed inshore locations (∼10-km radius) and remained there throughout the nonbreeding period (September– March). Two juveniles tagged at the breeding colony as fledglings remained at their wintering sites for the duration of the tracking interval (14 and 22 mo, respectively). Most cormorants used multiple sites within their winter ranges for roosting and foraging. Band recoveries show that Pelagic Cormorants in southern British Columbia and Washington disperse locally in winter, rather than migrating like the cormorants in our study. Radio-tagging and monitoring cormorants and other seabirds from known breeding sites are vital for understanding migratory connectivity and improving conservation strategies for local populations. RESUMEN Los factores que afectan la sobrevivencia durante el invierno podrian ser determinantes claves del estado y tendencias poblacionales de las aves marinas, pero las conexiones entre los sitios de reproduccion y las areas de invernada de la mayoria de las poblaciones es poco conocido. Phalacrocorax pelagicus (N = 6) con transmisores satelitales quirurgicamente implantados, migraron de una colonia reproductiva de la Isla de Middleton, en la parte norte del Golfo de Alaska, a sitios de invernada en el sudeste de Alaska y el norte de Columbia Britanica. Los sitios de invernada estuvieron a una distancia promedio de 920 km (rango = 600–1190 km) del sitio de reproduccion. Vuelos migratorios en el otono y la primavera duraron ≤5 dias en cuatro instancias. Despues de llegar a las areas de invernada, los P. pelagicus se quedaron en sitios especificos (con un radio de ∼10 km) que no estaban sobre la costa, y se quedaron ahi a traves del periodo no-reproductivo (Septiembre – Marzo). Dos juveniles que fueron marcados en la colonia reproductiva como volantones se quedaron en los sitios de invernada durante todo el seguimiento que hicimos (14 meses y 22 meses, respectivamente). La mayoria de los P. pelagicus usaron multiples sitios como dormideros y para forrajear en las areas de invernada. Las recuperaciones de anillos demuestran que los P. pelagicus en el sur de Columbia Britanica y Washington dispersan localmente en el invierno, en vez de migrar como los P. pelagicus en nuestro estudio. Colocar radiotransmisores a los P. pelagicus y a otras aves marinas en sitios reproductivos es vital para entender su conectividad migratoria y para mejorar las estrategias de conservacion para las poblaciones locales.