Leach's Storm-petrels Research Articles

Flexible Growth Rates in Fork-Tailed Storm-Petrels: A Response to Environmental Variability

We examined the degree that growth in Fork-tailed Storm-Petrel (Oceanodroma furcata) chicks varies among individuals and years. Data on wing chord length and body mass were collected on 10 or more chicks per year on the Barren Islands, Alaska, during seven years over two decades. In contrast to the apparently uniform growth rates in other storm-petrels (e.g. Leach's Storm-Petrel (Oceanodroma leucorhoa) and British Storm-Petrel (Hydrobates pelagi- cus)), Fork-tailed Storm-Petrel chicks on the Barren Islands displayed a two-fold variation in both wing growth and mass gain. Variation in growth rate was apparent both within and among years. Correlations between wing growth and mass gain were significant in only four of seven years, a finding we interpret as indicative of the importance of changes in food quality and quantity on growth. The decadal changes in growth rate of this species between the 1980s and 1990s are consistent with the regulating role that environmental variation appears to play in the growth and survival of storm-petrels. We suggest that the wide range of observed growth rates among individuals, years, and between decades is a response to environmental variability. Received 7 November 1996, accepted 9 June 1997.

Heavy metal and metallothionein concentrations in seabirds from the Pacific coast of Canada

Seabird tissues, collected during the 1990 breeding season from colonies on the Pacific coast of Canada, were analysed for Cd, Hg, Pb and 19 other trace elements. Metallothionein (Mt) was measured in kidneys of three species. Ranges of essential trace metal concentrations were generally narrow, consistent with homeostatic control of these elements in seabird tissues. Cadmium concentrations were always higher in kidney than in liver. Highest mean Cd concentrations (306±78 μg g −1 dry wt) were in kidneys of planktivorous Leach's storm-petrels ( Oceanodroma leucorhoa) from Hippa Island in the Queen Charlotte archipelago. Cadmium concentrations in kidneys of both Leach's storm-petrels and rhinoceros auklets ( Cerorhinca monocerata) were significantly greater at northern colonies compared to those further south. Cadmium and Mt concentrations were positively correlated in kidneys across the three species for which measurements were made [rhinoceros auklet, Cassin's auklet ( Ptychoramphus aleuticus), and ancient murrelet ( Synthliboramphus antiquus)] with an overall r = 0.82, p < 0.001. Mercury accumulation was not sufficiently great to be of toxicological concern in any of the 5 species. Highest mean Hg concentrations (6.37 μg g −1) were in livers of Leach's storm-petrels from Cleland Island on the west coast of Vancouver Island, and were significantly greater than in birds from further north on Hippa Island. Concentrations of hepatic Hg and Se were not correlated in the three species (rhinoceros auklet, Cassin's auklet and ancient murrelet) for which Se was measured. Lead concentrations were consistently greatest in bone, with highest mean concentrations in fork-tailed storm-petrels ( Oceanodroma furcata) (6.2 μg g −1 dry wt).

Effects of Circadian Rhythm and Breeding Stage on Resting Metabolic Rates in Fasting Leach's Storm-petrels.

The oxygen consumption of fasting Leach's Storm-petrels Oceanodroma leucorhoa was measured in captivity with a metabolic chamber at nest burrow temperature (16°C). The average mass-specific oxygen consumption of incubating birds (2.84ml/g/h at night and 2.10ml/g/h in day) was lower than that of chick rearing birds (3.31ml/g/h at night and 2.98ml/g/h in day). Three days of fasting did not affect mass-specific oxygen consumption. At each breeding stage mass-specific oxygen consumption was higher at night than during the day (1.1-1.3 times). In the wild, body mass of incubating birds (45.7±2.9 SDg) was greater than those rearing chicks (43.1±2.7 SDg). It appeared that incubating birds may tolerate fasting for the 3 day incubation spell by reducing resting metabolic rate and spending metabolic energy on body fat reserves.

Using Animal Behavior for Conservation

To develop successful restoration programs for wildlife, conservation biologists should consider features of animal behavior to help design restoration plans. This paper presents case studies of the first restored colonies of Arctic Terns (Sterna paradisaea), Common Terns (S. hirundo) and Roseate Terns (S. dougallii), Atlantic Puffins (Fratercula arctica) and Leach's Storm-Petrels (Oceanodroma leucorhoa). These restoration projects are based on the use of two fundamental and commonly occurring features of colonial waterbird behavior: social facilitation and philopatry.Social facilitation, the influence of one animal's behavior on that of its associates, was adapted for conservation purposes by placing decoys and sound recordings at historic nesting islands to simulate established colonies. The use of decoys and audio recordings to simulate and encourage social facilitation is referred to as social attraction. Philopatry, the tendency for young birds to recruit to nesting populations at their natal home, was adapted for conservation purposes by translocating puffin chicks from a large colony at the center of the range to historic nesting islands at the southern, historic limit of the puffin's range where they were extirpated nearly a century earlier by excessive hunting for food and feathers. Young puffins, reared and released from artificial burrows at two historic sites learned the location of the release sites and eventually returned to the long-extinct colonies rather than their hatching place.To restore colonies of terns and puffins that were displaced by Herring and Great Black-backed Gulls, nesting population of these gulls were reduced at Eastern Egg Rock and Seal Island National Wildlife Refuge (NWR) to encourage recolonization by terns and puffins. Common, Arctic and Roseate Terns were attracted to island recolonization sites off mid-coast Maine, USA using decoys and 24-hour playback recordings. By 1996, Seal Island NWR was the largest Arctic Tern colony in Maine with 956 pairs and Eastern Egg Rock was the largest Roseate Tern colony in the state with 126 nesting pairs of this endangered species. These successes using social attraction are compared to tern restoration on Petit Manan Island, Maine where gull control alone resulted in recolonization. In this example, terns were absent for only 4 years and many were still living with a memory of nesting on the island. After gull removal, these birds quickly recolonized in the same year that gull control began. In contrast, using gull control and social attraction, it took 3 and 5 years respectively for terns to re-colonize Eastern Egg Rock and Seal Island NWR (where terns had not nested for 44 and 36 years). In these cases, no living terns with a memory of nesting on these islands were available for recolonization.Puffin colonies at Eastern Egg Rock and Seal Island NWR were restored by translocating 3-40 (average 17) day-old puffin chicks from Newfoundland, Canada (approx. 1610km distant). A total of 954 and 950 chicks were translocated to Eastern Egg Rock and Seal Island NWR respectively. These were captive-reared in individual sod burrows which were opened at their entrance after the first week. The chicks were banded and permitted to fledge into the adjacent ocean. Translocated puffins began to return when two years old; many also visited nearby puffin colonies where some eventually nested. Recolonization at the historic nesting sites occurred in 1981 and 1992 respectively at Eastern Egg Rock and Seal Island NWR-in both cases 8 years after initiation of translocations. Four pairs nested in 1981, a number that increased to 19 pairs by 1985 and has remained constant at 16-19 pairs, due to recruitment of native-hatched chicks. At Seal Island NWR, 7 pairs nested in 1992 and increased to 40 pairs by 1996.

Short-eared Owl, Asio flammeus, predation on Leach's Storm-Petrels, Oceanodroma leucorhoa, in Massachusetts

Short-eared Owl, Asio flammeus, predation on Leach's Storm-Petrels, Oceanodroma leucorhoa, in Massachusetts

Monogamy in Leach's Storm-Petrel: DNA-Fingerprinting Evidence

We used multilocus minisatellite DNA fingerprinting to estimate the frequency of extrapair fertilizations in a population of Leach's Storm-Petrel (Oceanodroma leucorhoa) on Kent Island, New Brunswick, Canada. Leach's Storm-Petrel is a member of Procellariiformes, an order of long-lived pelagic birds characterized by long-term pairbonds, single-egg clutches, and extended periods of parental care. We found no evidence of extrapair fertilizations in 48 families (42 full families and 6 partial families consisting of the putative father and the single offspring). Thus, our results indicate that the breeding system (genetic monogamy) matches the mating system (social monogamy) in our study population, a condition that no longer can be assumed in socially monogamous bird species. Genetic monogamy in Leach's Storm-Petrels may be maintained by last-sperm precedence and frequent copulation by mates during the female's fertile period. Such tactics employed by a male may yield a high prob- ability of fertilizing the single egg laid by his mate. Received 15 June 1994, accepted 31 August

Petrel parents shunt all experimentally increased reproductive costs to their offspring

Investment in current reproduction should be balanced against future reproduction. Thus, the allocation of resources during a breeding season is a trade-off between the needs of the parent and the needs of the offspring. Life-history theory predicts the trade-off point to favour the parent in long-lived species and the offspring in short-lived species. To investigate parent-offspring conflict in a long-lived species, the cost of flight was manipulated (by reducing wing span) in Leach's storm-petrel,Oceanodroma leucorhoa. The effect of the manipulation on adult nutritional condition was measured using ptilochronology and the effect on offspring nutritional condition was measured by tracking chick growth. No difference was found in nutritional condition between treatment and control parents. Treatment chicks gained mass more slowly and spent a greater proportion of nights without being fed by either parent. As predicted for a long-lived species, when faced with an increased cost of parental care, the storm-petrel parents apparently shunted that cost to their offspring. These results are compared with previous studies of long- and short-lived species in which parental costs were artificially increased.

Foraging Stochasticity and Lipid Accumulation by Nestling Petrels

1. Procellariiform birds accumulate large fat reserves during the nestling period; much of this is metabolized prior to fledging. We suggest that these energy reserves result from chronic overfeeding, which provides insurance against stochastic variation in food provisioning. 2. We develop a simulation model based on food provisioning and physiological measurements of Leach's storm-petrels and assess fat accumulation as a function of meal size. The simulations reveal that a level of food provisioning sufficient for accumulating, on average, the fat reserves of a typical fledgling results in the starvation of many chicks because of the chance occurrence of long periods of below-average feeding

Leach's Storm-Petrels Prey On Lower Mesopelagic (Mysidacea and Decapoda) Crustaceans: Possible Implications for Crustacean and Avian Distributions

[Three species of rarely collected lower mesopelagic crustaceans (the mysid Eucopia grimaldii, and the decapods Sergestes arcticus and Hymenodora gracilis) were found in regurgitated parental food delivered to a breeding colony of Leach's storm-petrels off southern Newfoundland (46°53'N 56°05'W). The known distributions of these crustaceans are consistent with other deep water mesopelagic animals, such as myctophid fish that are the main prey of Leach's storm-petrels in southern Newfoundland. The occurrences of these deep water species as prey support previous contentions that these seabirds forage over deep water and also raises the possibility that these crustaceans may migrate nearer to the surface than previously indicated., Three species of rarely collected lower mesopelagic crustaceans (the mysid Eucopia grimaldii, and the decapods Sergestes arcticus and Hymenodora gracilis) were found in regurgitated parental food delivered to a breeding colony of Leach's storm-petrels off southern Newfoundland (46°53'N 56°05'W). The known distributions of these crustaceans are consistent with other deep water mesopelagic animals, such as myctophid fish that are the main prey of Leach's storm-petrels in southern Newfoundland. The occurrences of these deep water species as prey support previous contentions that these seabirds forage over deep water and also raises the possibility that these crustaceans may migrate nearer to the surface than previously indicated.]

The Treatment of Biologists by the U.S. Fish and Wildlife Service

The comments below by Dr. Russell P. Balda discuss difficulties biologists may experience regarding use of scientific collecting permits issued by the United States Fish and Wildlife Service (USFWS). This letter was submitted as a portion of an agreement between U.S. government attorneys and Dr. Balda. I publish Dr. Balda's comments with hesitation, because-as has been the case for other avian biologists in the recent past-it appears that federal officials are using their prosecution of Balda as a means to send a message to the scientific community. In one sense, I agree with these officials; ornithologists should be cognizant of the distorted priorities of the Law Enforcement Division of the USFWS. I will not describe Dr. Balda's alleged infractions, except that they involved collection of a few individuals of a common bird species. It is clear, however, that the federal action against him is by no means an isolated event. Consider, for example, the case of Dr. Nathaniel Wheelwright (Graham 1992). Wheelwright salvaged seven birds found dead in Canada and brought them to the United States. All were of common species: Tree Swallows, Savannah Sparrows, and a Leach's Storm-Petrel. Although Wheelwright had applied for a permit to import specimens, the Fish and Wildlife Service mistakenly wrote it to allow importation of only blood samples. Wheelwright, however, obtained oral consent from the USFWS to import the birds and declared them to that agency upon his return to the United States. Remarkably, he was later charged with violating the Migratory Bird Treaty Act, the Endangered Species Act, and the Lacey Act. During nine months of federal investigations, fines and jail terms were threatened and his collecting permit-vital for both his teaching and researchwas withheld. Pressure from the Maine congressional delegation eventually forced the U.S. attorney to drop criminal charges. The Fish and Wildlife Service, however, proceeded with civil actions and notified Wheelwright that he faced fines up to $75,000 for his salvage of the seven dead birds. Again, congressional pressure was required to end this harassment.

Renal response to saline infusion in chicks of Leach's storm petrel (Oceanodroma leucorhoa)

The renal response to infusion of three different saline solutions was studied in chicks of Leach's storm petrel (Oceanodroma leucorhoa). Each of the solutions (125 mmol·1-1 NaCl at 5.3 ml·h-1, 250 mmol·l-1 NaCl at 2.6 ml·h-1, and 550 mmol·l-1 NaCl at 1.2 ml·h-1) provided the same delivery of Nacl but in different volumes of water. Birds infused with 125 mmol·l-1 NaCl had a glomerular filtration rate of 25.7 ml·h-1, a urine flow rate of 4.4 ml·h-1, and excreted 71% of the infused Na+ load in the urine. With infusion of 250 mmol·l-1 NaCl, the glomerular filtration rate was unchanged (23.3 ml·h-1), but urine flow rate was reduced to 0.93 ml·h-1 and only 35% of the Na+ load was excreted in the urine. Infusion of 550 mmol·l-1 NaCl induced a sharp decrease in glomerular filtration rate (to 3.8 ml·h-1) and urine flow rate (to 0.08 ml·h-1), and only 1.4% of the infused Na+ was excreted in the urine. The contribution of different nephron populations to filtration was assessed by the pattern of staining of glomeruli by alcian blue infused during the last 30 min of the saline infusion. The numbers of stained glomeruli did not differ between birds infused with 125 and 250 mmol·l-1 NaCl (59000 and 55000 glomeruli per kidney, respectively), and the patterns of staining were similar for birds in these two groups. Birds infused with 550 mmol·l-1 NaCl had lighter staining overall and fewer stained glomeruli (37000 per kidney). This absence of staining was predominant in the smaller size classes of glomeruli, suggesting a selective shutdown of smaller (reptilian-type) nephrons during times of osmotic challenge in these birds. This may be part of an overall suite of water-conserving strategies employed by these chicks during their long confinement with irregular feeding in the nesting burrow.

Vocalizations of Nestling Leach's Storm-Petrels

teractions of the Shiny Cowbird and the Yellowshouldered Blackbird. Condor 79:176-184. ROBINSON, S. K. 1986. Benefits, costs, and determinants of dominance in a polygynous oriole. Anim. Behav. 34:241-255. ROBERTSON, R. J., AND R. F. NORMAN. 1976. Behavioral defenses to brood parasitism by potential hosts of the Brown-headed Cowbird. Condor 78: 166-173. ROTHSTEIN, S. I. 1977. The preening invitation or head-down display of parasitic cowbirds: I. Evidence for intraspecific occurrence. Condor 79:1323. ROTHSTEIN, S. I. 1980. The preening invitation or head-down display of parasitic cowbirds: II. Experimental analysis and evidence for behavioural mimicry. Behaviour 75:148-184. ROTHSTEIN, S. I., D. A. YOKEL, AND R. C. FLEISCHER. 1986. Social dominance, mating and spacing syst ms, female fecundity, and vocal dialects in captive and free-ranging Brown-headed Cowbirds. Curr. Ornithol. 3:127-185. SCOTT, T. W., AND J. M. GRUMSTRUP-SCOTT. 1983. Why do Brown-headed Cowbirds perform the head-down display? Auk 100:139-148. SELANDER, R. K. 1964. Behavior of captive South American cowbirds. Auk 81:394-402. SELANDER, R. K., AND C. J. LA RUE, JR. 1961. Interspecific preening invitation display of parasitic cowbirds. Auk 78:473-504. WEATHERHEAD, P. J., AND D. J. HOYSAK. 1984. Dominance structuring of a Red-winged Blackbird roost. Auk 101:551-555. WILEY, J. W. 1985. Shiny cowbird parasitism in two avian communities in Puerto Rico. Condor 87: 165-176.

Chitin Digestion and Assimilation by Seabirds

As a structural component of crustacean exoskeletons, chitin is the most important carbohydrate in the diets of many marine carnivores. To investigate the physiological and biochemical adaptations that may enable seabirds to break down this “prey defense,” we estimated chitin digestibilities for Sooty Albatrosses (Phoebetria fusca), White-chinned Petrels (Procellaria aequinoctialis), Rockhopper Penguins (Eudyptes chrysocome), Gentoo Pen­ guins (Pygoscelis papua), King Penguins (Aptenodytes patagonicus) and Leach's Storm-Petrels (Oceanodroma leucorhoa) fed Antarctic krill (Euphausia superba). These species retain a substantial proportion (46.5 ± SD of 13.1%, 39.1 ± 4.9%, 52.8 ± 37.6%, 45.3 ± 5.6%, 84.8 ± 11.7% and 35 ± 12.2%, respectively) of ingested chitin. We also obtained preliminary estimates of chitinolytic activity in the gastric mucosae of the above six species by incubating extracts of tissue samples with a chitin substrate and measuring the production of the end product of chitin hydrolysis, N-acetyl-D-glucosamine (NAG). Chitinolytic activity (up to 5,000 11-g NAG h- 1 g-1 expressed per gram tissue) was measured from proventricular tissue and within the activity range (1,350 to 61,650 11-g NAG h- 1 g- 1) reported for eight other avian species. In order to assess the energetic and nutritional benefits of chitinolytic activity in seabirds, we studied gastrointestinal absorption of the end products of chitinolysis in Leach's Storm­ Petrels. The overall absorption efficiency of NAG and its deacetylated precursor, glucosamine (Gln), in this species was 44.0 ± 3.0% and 11.0 ± 1.9%, respectively. These absorption effi­ ciencies were significantly less than for glucose, which was absorbed with an efficiency of 90.6 ± 2.5%. No absorption of NAG and Gln occurred in the proventriculus. Overall, we showed that seabirds have a capacity to assimilate a considerable portion of the carbon and nitrogen present as chitin in the exoskeleton of their prey, but we have not demonstrated that assimilation actually occurs. The potential costs and benefits of chitin hydrolysis, as well as the absorption of the breakdown products, need to be assessed.

Bile is essential for lipid assimilation in Leach's storm petrel, Oceanodroma leucorhoa.

A tritium-labeled glycerol triether was tested as a non-absorbable lipid marker for studies of neutral lipid absorption in normal and cholestryamine-induced steatorrhic chicks of Leach's storm petrel (Oceanodroma leucorhoa). Absorption of triacylglycerol and wax ester (96 +/- 4.2 and 94 +/- 2.1%, respectively) in normal chicks was indistinguishable. Absorption of neutral lipids decreased with increasing quantities of resin, and with the highest dosage (14% wt/wt) less than 30% of dietary lipids were assimilated. The concentration of bile salts (greater than 500 mM) in the gallbladder of Leach's storm petrel is among the highest recorded. The bile salts are predominantly taurine conjugates of chenodeoxycholate and cholate. Biliary cholesterol levels are within the range observed in humans although biliary phospholipid levels are lower and triglyceride levels are higher. Extensive retrograde movement of duodenal contents and biliary secretions to the gizzard and proventriculus were found. Although similarities in fat and bile salt assimilation exist between seabirds and mammals, there do exist differences that make non-polar lipid assimilation (i.e., wax esters) more efficient in seabirds.

Reproductive Energetics and Prey Harvest of Leach's Storm‐Petrels in the Northwest Atlantic

Leach's Storm—Petrels (Oceanodroma leucorhoa), the smallest and most abundant seabirds that breed in the northwest Atlantic, are not usually included in avian energetics models. To round out an energy analysis of seabirds spanning the full range of body sizes in the northwest Atlantic, the field metabolic rates (FMRs) of breeding Leach's Storm—Petrels were measured using doubly labeled water techniques (DLW). Metabolic, dietary and, demographic data were used as inputs in a populations energetics model to estimate the energy requirements and prey harvests of the Leach's Storm—Petrel population of eastern North America. FMRs of storm—petrels that remained in burrows averaged 83.3 ± 19.4 KJ/d. FMRs increased significantly with time (i.e., x in hours per day) at sea (y = [85.8 ± 6.5] + [3.13 ± 0.48]x), and metabolism at sea was estimated to be 161 ± 18 KJ/d. FMRs integrated over activity on land and activity at sea averaged 124 KJ/d during incubation and 142 KJ/d during chick rearing. Incubating adults weighed significantly more than adults rearing chicks, although adult mass did not vary with age of chick. Basal metabolic rate (BMR, measured as O2 flux) averaged 2.02 ± 1.01 cm3°g—1°h—1, equivalent to 45.4 ± 30.4 KJ/d, very similar to values obtained for breeding conspecifics in the Bay of Fundy and in the Bering Sea. Thermal conductance averaged 0.124 ± 0.065 cm3°g—1°h—1°°C—1. FMR/BMR ratios averaged 2.73 for incubating birds and 3.13 for birds rearing young. Population energetics modelling indicated that during a 7—mo breeding period Leach's Storm—Petrels at colonies in the northwest Atlantic Ocean consume &gt;74 000 Mg of prey, mostly myctophids and amphipods (mostly Hyperia galba), as wall as euphausiids (mostly Meganyctiphanes norvegica) and other prey (decapods, copepods, isopods). Leach's Storm—Petrels make up °80% of the breeding seabird population in eastern Canada, but owing to small body size and metabolic efficiency, they account for comparatively little of the energy that flows through the avian assemblage of the northwest Atlantic. An intra—specific, inter—colony difference in FMR is suggested: FMRs measured in a Newfoundland colony were significantly higher than those determined with the same DLW procedure in the Bay of Fundy near the southern limit of the species' breeding range in the northwest Atlantic. Differences in ambient temperatures and wind speed associated with different oceanographic regimes may generate energetic differences. Like inter—colony differences in feeding ecology, inter—colony differences in FMR need to be considered in population and community energetics models and in meso— and mega—scale extrapolations.

The roles of parent and chick in determining feeding rates in Leach's storm-petrel

Leach's storm-petrels rear only one chick per brood, and therefore sibling competition cannot be a factor in the evolutionary maintenance of food-solicitation behaviour. Several experiments were conducted to determine whether solicitation may none the less convery information about level of nutrition and thus influence feeding rate. Chicks were switched among nests at random at 40±1 days of age, approximately 3 weeks prior to the termination of parental feeding. Serial correlations were then calculated between each chick's weight before the switch and its weight during subsequent, age intervals, and between each chick's weight before the switch and that of the foster chick during subsequent age intervals. The results contradicted both chick-solicitation and parental-determination models of feeding. Experimental food deprivation suggested that parents do not respond to undernourishment of their chicks by increasing feeding rate. Furthermore, diet supplementation indicated that the rate at which chicks can process meals, especially their lipid component, may be limited by the assimilatory capacity of the digestive tract. The absence of a direct connection between solicitation and food provisioning in storm-petrels may reflect the low correlation between the recent feeding history of a chick and its subsequent requirements. Although solicitation behaviour may facilitate the transfer of food from the adult to the chick, it either does not convey information about nutritional status, or parents do or parents do not or cannot act upon that information.

The roles of parent and chick in determining feeding rates in Leach's storm-petrel

Leach's storm-petrels rear only one chick per brood, and therefore sibling competition cannot be a factor in the evolutionary maintenance of food-solicitation behaviour. Several experiments were conducted to determine whether solicitation may none the less convery information about level of nutrition and thus influence feeding rate. Chicks were switched among nests at random at 40±1 days of age, approximately 3 weeks prior to the termination of parental feeding. Serial correlations were then calculated between each chick's weight before the switch and its weight during subsequent, age intervals, and between each chick's weight before the switch and that of the foster chick during subsequent age intervals. The results contradicted both chick-solicitation and parental-determination models of feeding. Experimental food deprivation suggested that parents do not respond to undernourishment of their chicks by increasing feeding rate. Furthermore, diet supplementation indicated that the rate at which chicks can process meals, especially their lipid component, may be limited by the assimilatory capacity of the digestive tract. The absence of a direct connection between solicitation and food provisioning in storm-petrels may reflect the low correlation between the recent feeding history of a chick and its subsequent requirements. Although solicitation behaviour may facilitate the transfer of food from the adult to the chick, it either does not convey information about nutritional status, or parents do or parents do not or cannot act upon that information.

Heavy metal and metallothionein concentrations in Atlantic Canadian seabirds.

Seabird tissues, collected during the 1988 breeding season from colonies on the Atlantic coast of Canada, were analyzed for toxic metals--Cd, Hg and Pb--and 18 other trace elements. Metallothionein (MT) was measured in kidney, and kidneys and livers underwent histopathological examination. Levels of most essential trace elements appear to be closely regulated in seabird tissues; values were in good agreement with those previously reported in the published literature. Liver-Se concentrations in Leach's storm-petrels (Oceanodroma leukorrhea) (77.6 + 7.49 micrograms/g dry weight) were much higher than values normally reported for free-living birds and mammals. Cd levels varied greatly among individuals, but were always higher in kidney than in liver. Highest mean Cd concentrations (183 + 65 micrograms/g dry weight) were in kidneys of the planktivorous Leach's storm-petrels from the Gulf of St. Lawrence. A few individuals of this species had values greater than 300 micrograms/g dry weight. Cd and metallothionein (MT) concentrations were positively correlated in kidneys of Leach's storm-petrels (r = 0.692), Atlantic puffin (Fratercula arctica) (r = 0.845) and herring gull (Larus argentatus) (r = 0.866). Concentrations of total Hg varied greatly among species and individuals, but were consistently higher in liver than in kidney. Highest mean levels (21 + 28 micrograms/g) were in livers of the piscivorous double-crested cormorant (Phalacrocorax auritus) from Saint John Harbour in the Bay of Fundy. Concentrations of Hg and Se were positively correlated (r = 0.736) in livers of Leach's storm-petrel, but not in other species. Pb concentrations were consistently greatest in bone, with mean levels being highest in herring gulls from a colony in the Bay of Fundy (63 + 36 micrograms/g). Histological examination of liver and kidney failed to reveal indications of tissue damage associated with elevated levels of heavy metals.

The Volume of Stomach Oils Increases during Prefledging Weight Loss in Leach's Storm-Petrel (Oceanodroma leucorhoa) Chicks

We have investigated the physiological mechanisms responsible for stomach oil accumulation unique to the Procellariiformes (Duke et al. 1989; Roby et al. 1986, 1989; Place et al. 1986, 1989; Jackson and Place 1990). An earlier study with Leach's Storm-Petrel (Oceanodroma leucorhoa) reported that chicks near fledging (55 days and older) accumulate greater volumes of stomach oil than younger chicks (Place et al. 1989). To better document the age of onset of oil accumulation, we measured the volume of stomach oil in 38 chicks of known hatching date throughout the 1989 breeding season on Little Duck Island, Maine (44?10'N, 68?15'W). The volume of stomach oil in 20 chicks was measured once at ages varying from 14 to 69 days. The volume in 15 chicks was measured at ages 25.3 days (SE = 1.5), 42.0 days (SE = 1.4), and 58.5 days (SE = 1.5). Three additional chicks fledged before a third sampling could be performed. We determined stomach oil volume by dilution of a tritium-labeled glycerol triether ([3H]-GTE), a nonabsorbable, nonmetabolizable lipid-phase marker (Place et al. 1989). Chicks were fed 0.5 cc of olive oil that contained 1.3 MCi/ml of 3H-GTE. We sampled the proventricular lipids, after periods of 1-3 h. Stomach oils were separated from aqueous and particulate phases by centrifugation at 10,000 x g for 10 min before samples were removed for scintillation counting and lipid analysis (Place et al. 1989). A minimum of 2 h was needed to ensure complete equilibration of the tracer (i.e. constant specific activity) with endogenous lipids. To validate the volume estimation technique, we prepared a set of artificial stomach oils by adding increasing quantities of olive oil (0-9 ml) to 1 ml of avian Ringer's in 15 ml conical centrifuge tubes. The oil-Ringer's mixture was vortexed to produce an unstable milky emulsion. Labeled olive oil (0.5 ml) was delivered to each tube by the same procedure as performed in the field. The artificial stomach oils were mixed by hand agitation and sampled 2 h later as described for authentic stomach oils. The volume of the lipid phase can be estimated by this technique with a high degree of precision (Fig. 1). Our study covered >90% of the nestling growth period in Leach's Storm-Petrel chicks (Fig. 2: A and B), and includes the last 15 days before fledging when chick mass decreases (Ricklefs et al. 1980a, 1980b). Stomach oils were found in all chicks sampled, and the volume of stomach oil was highly variable within any age group (Fig. 2C). A repeated-measure ANOVA showed no significant between-bird variation in the 15 chicks sampled repeatedly (F14, , = 731.4, P 0.728), but there was a highly significant (F2,44 = 11.94, P < 0.0002) age effect on the volume of stomach oil. When the data from all 38 chicks were grouped into 5-day age intervals, a one-factor ANOVA revealed a significant effect (F10,78 = 6.64, P < 0.0001) when contrasting the volume of oil in each group. In pairwise comparisons, there was a significant difference (P c 0.05) between the volume of oil in chicks of age groups 60-64 days and 65-69 days, and chicks of all other age groups. After 60 days of age, the mean volume of oil (6.3 ? 2.9, n 25) increased nearly threefold when compared with the mean volume of oil in the previous 54 days (2.3 ? 1.8, n = 52). Earlier stomach oil volume estimates for Leach's Storm-Petrel chicks (1.2 ? 0.9 ml, 39.4 ? 0.5 days, n = 12 [Place and Roby 1986]; 8.3 ? 1.6, n = 12, 65-70 day old chicks [Place et al. 1989]) are consistent with the present estimates. This accumulation of stomach oils occurs when chick body mass decreases, primarily from reductions in

Sexual Differences in Flight Calls and the Cue for Vocal Sex Recognition of Swinhoe's Storm-Petrels

Previous studies have shown that the Flight Calls of Swinhoe's Storm-Petrels (Oceanodroma monorhis) differ clearly between the sexes in their frequency component and that birds can discriminate the calls of either sex with few errors (Taoka et al. 1989b). But the cue for sex recognition has not yet been identified. In this study, we quantitatively analyzed the calls of both sexes for call length, number of syllables, and duration and interval of syllables. We found some sexual differences in rhythmic components, but mean ? standard deviation overlapped in all syllables. In order to make synthetic calls for playback experiments, frequency and rhythmic components were systematically manipulated. Birds recognized the synthetic calls having the same harmonic structure as female calls but those without harmonic structure were recognized as male calls regardless of whether the rhythm was that of the female or the male. Therefore, we concluded that harmonic structure is the cue for sex recognition. The mechanism of vocal sex recognition was compared with that of the closely related species, the Leach's Storm-Petrel (0. leucorhoa).