Leach's Storm-petrels Oceanodroma Research Articles

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Shifting prey availability can lead to altered species interactions, indicated by variation in the dietary niche breadth and position of species within an assemblage. On the Newfoundland coast, annual inshore spawning migration of the dominant forage fish, CapelinMallotus villosus, provides an excellent opportunity to investigate the influence of varying prey availability on dietary niche breadth and position among species. During June–August 2017, we investigated species‐ and assemblage‐level dietary responses to shifting Capelin availability of three Capelin‐eating, sympatrically breeding auk species, the Atlantic PuffinFratercula arctica, RazorbillAlca tordaand Common MurreUria aalge. The diet of Leach's Storm PetrelsOceanodroma leucorhoa, which breed alongside the three auk species but are not known to rely on Capelin, was also examined to determine dietary shifts throughout breeding that were unrelated to Capelin availability. We quantified stable isotope ratios (δ15N, δ13C) in seabird blood components (plasma, cellular component) collected both before and after spawning Capelin arrived in the study area and compared isotopic niche breadth within a Bayesian framework. At the species level, auk trophic position increased and isotopic niche breadth narrowed after Capelin arrived, suggesting a more Capelin‐based diet. Simultaneously, trophic diversity of the auk assemblage, reflecting the extent of spacing among niches of species, decreased after spawning Capelin arrived inshore. Contrastingly, increased trophic position but broader isotopic niche breadth during higher relative to lower Capelin availability for Leach's Storm Petrel confirm that this species is probably not affected by the inshore arrival of Capelin, but instead that isotopic changes may be more related to a shift in breeding stage to chick‐rearing. Overall, our findings reiterate the importance of Capelin as a prey resource for breeding auks in coastal Newfoundland, but that the degree of reliance on Capelin varies among species, possibly allowing coexistence of these ecologically similar species. The findings highlight potential changing species interactions, such as increased competition, under declines in Capelin biomass.

Finding the best predictor of reproductive performance of Leach's Storm-Petrels

ABSTRACT Physiological and environmental factors shape foraging strategies and energy balance. For species that breed seasonally, physiological changes in an individual can have short-term effects, but also can persist as carry-over effects from one season to the next, such as from the overwintering season to the breeding season. We tested the hypothesis that reproductive performance could be predicted by diet and energy balance during the breeding and nonbreeding seasons in a long-lived seabird, the Leach's Storm-Petrel (Oceanodroma leucorhoa). Specifically, we predicted that better reproductive performance would be correlated with four factors: (1) a high-lipid diet, as indexed by a high C:N ratio in stable isotope analyses; (2) a diet rich in antioxidants, as indexed by high plasma antioxidant capacity; (3) foraging at a high trophic level, as indexed by high values of δ15N in stable isotope analyses, which is positively related to lipids; and (4) a positive long-term energy balance, revealed by low le...

Population genetic structure and long‐distance dispersal among seabird populations: Implications for colony persistence

Dramatic local population decline brought about by anthropogenic-driven change is an increasingly common threat to biodiversity. Seabird life history traits make them particularly vulnerable to such change; therefore, understanding population connectivity and dispersal dynamics is vital for successful management. Our study used a 357-base pair mitochondrial control region locus sequenced for 103 individuals and 18 nuclear microsatellite loci genotyped for 245 individuals to investigate population structure in the Atlantic and Pacific populations of the pelagic seabird, Leach's storm-petrel Oceanodroma leucorhoa leucorhoa. This species is under intense predation pressure at one regionally important colony on St Kilda, Scotland, where a disparity between population decline and predation rates hints at immigration from other large colonies. AMOVA, F(ST), Φ(ST) and Bayesian cluster analyses revealed no genetic structure among Atlantic colonies (Global Φ(ST) = -0.02 P > 0.05, Global F(ST) = 0.003, P > 0.05, STRUCTURE K = 1), consistent with either contemporary gene flow or strong historical association within the ocean basin. The Pacific and Atlantic populations are genetically distinct (Global Φ(ST) = 0.32 P < 0.0001, Global F(ST) = 0.04, P < 0.0001, STRUCTURE K = 2), but evidence for interocean exchange was found with individual exclusion/assignment and population coalescent analyses. These findings highlight the importance of conserving multiple colonies at a number of different sites and suggest that management of this seabird may be best viewed at an oceanic scale. Moreover, our study provides an illustration of how long-distance movement may ameliorate the potentially deleterious impacts of localized environmental change, although direct measures of dispersal are still required to better understand this process.

Relationship between Body Water and Lipid in Three Seabird Species: Leach's Storm-Petrel, Rhinoceros Auklet and Black-Tailed Gull

Abstract Measuring the individual body conditions of living birds is essential for understanding tradeoffs in life-history studies, especially in long-lived species. The aim of this study was to further develop a method for measuring body condition (lipid content), without killing birds. In theory, the lipid content mass in the body should have a close inverse relationship with water mass. Using this relationship, body condition can be evaluated without killing because the amount of water in the body can be estimated in live birds. However, the inverse relationship has only been shown to exist in a few studies of bird species. In this study, significant inverse relationships between water and lipid contents of three seabird species, Leach's Storm-Petrel Oceanodroma leucorhoa, Rhinoceros Auklet Cerorhinca monocerata and Black-tailed Gull Lams crassirostris, were shown. These facts highlight that body condition (lipid content) , can be estimated from the water content of the body.

Maximum Load-Carrying During Takeoff of Leach's Storm-PetrelOceanodroma leucorhoaand Cassin's AukletPtychoramphus aleuticus

Abstract. Birds at-sea increase body mass as a consequence of food consumption and plumage wettability. However, little is known about the effect of maximum extra load on takeoff of aquatic birds. Experimental evaluation of maximum load-lift during takeoff was performed on a wing-propelled diver with high wing loading, Cassin's Auklet Ptychoramphus aleuticus, and on a surface feeder with low wing loading, Leach's Storm-Petrel Oceanodroma leucorhoa. Leach's Storm-Petrel supported a maximum extra load of 45% of its body mass, and that of Cassin's Auklet was 25%. The relation of maximal load to food transport and plumage wettability indicates that the storm-petrel and the alcid maintain safety load margins of 31% and 8% of the maximum supported extra load during takeoff, respectively. Load margin showed by storm-petrels suggests an enhanced flight performance, increasing specific lift during foraging; meanwhile that of auklets allows for reduction of specific buoyancy during diving.

Seabird numbers and prey consumption in the North Atlantic

Abstract We compared seasonal composition, abundance, and biomass of seabirds between the Northeast (ICES region) and Northwest (NAFO region) Atlantic fisheries regions to identify differences in community assemblage and prey consumption. Seabirds were more abundant in the Northwest Atlantic, but biomass was greater in the Northeast. This disparity resulted from enormous numbers of little auks Alle alle breeding in West Greenland and of Leach's storm-petrels Oceanodroma leucorhoa breeding in Newfoundland, plus large numbers of non-breeding shearwaters Puffinus spp. entering southern NAFO areas in summer. The Northeast Atlantic communities were dominated numerically by northern fulmars Fulmarus glacialis, large auks Uria spp., and the Atlantic puffin Fratercula arctica. Seabirds occupying the North Atlantic consume approximately 11 × 106 t of food annually. Overall consumption rates peak during summer as a result of increased breeding activity and seasonal movements of birds into the North Atlantic. Because of the greater biomass of birds in the northeast, consumption (mainly by piscivores) in ICES areas was approximately 20% higher than that in NAFO areas, where planktivores dominate. NAFO areas had, however, a much greater consumption rate per unit area than ICES areas. Comparative studies such as these could prove informative in assessing large predator responses to the influence of fishing and ocean-scale climate change.

Effects of investigator disturbance on hatching success and nest-site fidelity in a long-lived seabird, Leach's storm-petrel

Long-lived animals are expected to reduce reproductive effort when breeding conditions are unfavorable, therefore seabirds may be especially sensitive to investigator disturbance. In a non-threatened procellariiform, Leach's storm-petrel Oceanodroma leucorhoa, we examined whether the frequency and the time of day of investigator disturbance influenced hatching success, and if disturbance affected hatching success and nest-site fidelity in the subsequent breeding season. Birds used in this study had received little or no investigator disturbance during the prior decade. Hatching success was significantly influenced by the frequency, but not the time of day, of disturbance. Weekly and daily handling of parents reduced hatching success by 50 and 56% compared to the control group. Most failures (91%) were caused by egg desertion, and all the deserted eggs belonged to pairs in the weekly and daily groups. During the subsequent breeding season, the hatching success of disturbed pairs that continued to breed together returned to normal levels. However, 37% more disturbed pairs than control pairs deserted the nesting burrows they had used in the previous year. Since most changes in nest site also result in mate change, investigator disturbance may have had long-term negative effects on reproductive success as well. Our results demonstrate that both weekly and daily investigator disturbance during incubation greatly reduced the hatching success and subsequent nest-site fidelity of naı̈ve Leach's storm-petrels.

Leach's storm petrels Oceanodroma leucorhoa off southern Africa: breeding and migratory status, and measurements and mass of the breeding population

Leach's storm petrel Oceanodroma leucorhoa have bred at Dyer Island since at least 1995; a review of earlier records in the light of this discovery indicates that breeding has almost occurred since at least the 1970s. The South African offshore islands on which Leach's storm petrel almost certainly breeds are Jutten, Dassen, Dyer and St Croix. The South African population is probably of the order of 25 pairs. The migrant component of the Leach's storm petrel population visiting southern Africa is mainly confined to deep ocean waters (generally 2000–5000 m deep) and occurs in particularly high densities around Agulhas Rings where ring-edges apparently provided excellent foraging opportunities. Leach's storm petrels are comparatively scarce over the shelf areas (defined as coastal water of less than 2000 m depth) of Namibia and western South Africa. Given their abundance at sea, their distance offshore, the seasonality of their occurrence and their moult status, these birds cannot be part of the South African breeding population, and must therefore be mainly from colonies of the north Atlantic Ocean. The Leach's storm petrels breeding in South Africa appear to be relatively large, comparable in size to populations breeding in the north Atlantic Ocean. Molecular techniques should be used to determine the most closely related population, and possibly the period for which the South African population has been isolated.

Changes in nesting-habitat use of large gulls breeding in Witless Bay, Newfoundland

We counted herring gull (Larus argentatus) and great black-backed gull (Larus marinus) nests in the Witless Bay Seabird Ecological Reserve in southeastern Newfoundland, Canada, in 1999 and 2000 and compared our results with previous nest counts from the 1970s. On Gull Island, herring gull nest numbers were 27.5% (1999) and 30.0% (2000) lower than in 1979. Similarly, on Great Island, by 2000 the numbers of herring gull nests had declined 40.8% from numbers in 1979. Counts of great black-backed gull nests were more variable, but suggest a slight or no reduction since 1979. Numbers of herring gulls nesting in rocky and puffin-slope habitats were much reduced (50–70%), while numbers nesting in meadows and forests have actually increased since the 1970s. Great black-backed gulls showed a similar change in nesting distribution. For herring gulls, these changes in nesting numbers matched differences in reproductive success previously documented in these habitats. We suggest that the decline in gull numbers and the change in breeding-habitat selection were caused by changes in the food availability for gulls. Reduced amounts of fisheries offal and the delayed arrival onshore of capelin (Mallotus villosus), an important fish prey species for gulls, have all likely led to the decline in gull reproductive output. Gulls nesting in meadows and forests may be maintaining adequate reproductive output by focusing on alternative prey, such as adult Leach's storm-petrels (Oceanodroma leucorhoa), rather than scarce refuse and fish.

Marine Bird Attraction to Thermal Fronts in the California Current System

AbstractI relate marine bird density to the 55 strongest thermal fronts encountered during a survey of much of the eastern portion of the California Current and the adjacent coastal upwelling region. Elevated densities were recorded for all marine bird taxa except the Leach's Storm-Petrel (Oceanodroma leucorhoa). The variance explained by the regression models ranged from 3% for the Leach's Storm-Petrel to 85% for all marine birds. The response observed is notably stronger than previous analyses with similar data.

First recorded breeding of Leach's Storm Petrel Oceanodroma leucorhoa in the Southern Hemisphere, at Dyer Island, South Africa

First recorded breeding of Leach's Storm Petrel Oceanodroma leucorhoa in the Southern Hemisphere, at Dyer Island, South Africa

Indirect effects of the availability of capelin and fishery discards:gull predation on breeding storm-petrels

The Northwest Atlantic has undergone large-scale perturbations which have had profound effects on pelagic food webs. Over the past century, the increasing availability of human refuse and fishery discards have promoted the growth of Larus gull populations. During the 1990s, cold surface-water events have delayed the inshore movements of spawning capelin Mallotus villosus and fisheries closures have eliminated massive tonnages of discards. These circumstances have interacted to intensify food stress on gulls. We investigated gull predation in a large colony of Leach's storm-petrels Oceanodroma leucorhoa as an indirect consequence of the availability of prey and fishery discards. Predation did not differ between storm-petrels nesting in forest and open habitats even though gull nests were more often in close proximity to storm-petrel burrows in open habitat. In 1996 and 1997, gull predation on storm-petrels varied seasonally, with a significant decrease following the inshore movement of spawning capelin, a primary food that gulls consume and feed to their chicks. Capelin availability occurred considerably later in 1997, when gull predation on storm-petrels was greater and prolonged. The intensity of gull predation on storm-petrels appears to depend on the availability of spawning capelin inshore.

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.

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.

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

Heterosexual response to playback calls of the Leach's Storm-Petrel Oceanodroma leucorhoa.

Four calls of the Leach's Storm-Petrel (Oceanodroma leucorhoa), the Chatter-calls and Purr-calls of both sexes, were played back from a loudspeaker on the ground near the colony in Daikoku Island. All the playback calls attracted birds in flight and elicited Chatter-calls from them. The sex of the attracted birds were judged by analyzing the Chatter-calls. Significantly more birds responded to the playback call of the opposite sex than that of the same sex. It has already been revealed that birds inside burrows respond only to the playback calls of the same sex. Therefore, in this study it was found that the same call can elicit responses from different sexes in different circumstances. Thus, the same call can have different meanings in different contexts.

Regional difference in the diet of slaty-backed gulls breeding around Hokkaido.

Regional difference in the diet of Slaty-backed Gulls, Larus schistisagus was studied at the colonies around Hokkaido, Japan. They fed their chicks with sardines Sardinops melanosticta, rock fish Sebastes spp., and seabird chicks on Teuri Island, sardines on Daikoku Island and sardines and sandlances Ammodytes sp. on Yururi Island. They preyed upon chicks of seabirds such as Black-tailed Gulls L. crassirostris, Rhinoceros Auklets Cerorhinca monocerata and conspecifics on Teuri Island, while they preyed upon adults of Leach's Storm-Petrels Oceanodroma leucorhoa on Daikoku, Yururi and Moyururi Islands. Although availability of conspecific chicks was higher on Daikoku, Yururi and Moyururi Islands than on Teuri Island, they preyed upon conspecific chicks more frequently on Teuri Island than on Daikoku, Yururi and Moyururi Islands. Thus, availability of conspecific chicks did not explain the regional difference in the occurrence of predition attempts on conspecific chicks.

THE SEASONAL OCCURRENCE OF LEACH'S STORM PETREL OCEANODROMA LEUCORHOA AT ST CROIX ISLAND, SOUTH AFRICA

Summary Randall, R. M. & Randall, B. M. 1986. The seasonal occurrence of Leach's Storm Petrel Oceanodroma leucorhoa at St Croix Island, South Africa. Ostrich 57: 157–161. Leach's Storm Petrel Oceanodroma leucorhoa vocalizations were heard regularly from late October to late January at night at St Croix Island. Initial identification based on vocalizations was confirmed following live trapping at a burrow. Behaviour was similar to that on northern hemisphere breeding grounds, but only one individual appeared to visit the island. Some individuals of the species probably migrate regularly to southern Africa, but the scarcity of such records may be due to their oceanic distribution and nocturnal island visits.