Larus Dominicanus Research Articles

Kelp gulls prey on the eyes of juvenile Cape fur seals in Namibia

The kelp gull Larus dominicanus is an abundant and highly successful avian predator and scavenger that breeds along the coastline in the Southern Hemisphere, ranging from Antarctica to the tropics. On account of its dietary breadth, wide-ranging foraging strategies, and acclimation to modified landscapes, this species has received considerable attention within the seabird literature over the past 40 years. Furthermore, owing to its ready habituation to human-dominated environments, the species has been used as a bio-indicator of habitat modification. Here we describe new predatory behaviours of the kelp gull on a larger-bodied sympatric mammal species, the Cape fur seal Arctocephalus pusillus pusillus, along the coast of Namibia, and discuss our findings as they relate to food web dynamics and behavioural plasticity.

Protection and provisioning: the role of parental behaviour in terms of chick growth and survival in a pelagic seabird

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 530:153-162 (2015) - DOI: https://doi.org/10.3354/meps11317 Protection and provisioning: the role of parental behaviour in terms of chick growth and survival in a pelagic seabird Gavin M. Rishworth*, Pierre A. Pistorius DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology, Nelson Mandela Metropolitan University, Summerstrand 6031, South Africa *Corresponding author: gavin.rishworth@gmail.com ABSTRACT: Long-lived organisms maximise lifetime reproductive output by shifting the negative effects of temporal environmental variability onto their offspring while maintaining adult survival. Amongst seabirds, chick growth and survival could be influenced by a range of factors, including prey delivery and parent behaviour as well as predation and exposure to adverse weather conditions. In this study, an automated method of recording adult Cape gannet Morus capensis time-activity budgets by means of new generation VHF technology was used to relate their behaviour to chick growth and survival at Bird Island, Algoa Bay, South Africa, across 2 breeding seasons (2011-2012 and 2012-2013). Using one of the most comprehensive datasets of breeding seabird foraging effort, we showed that, although chick growth was predominantly associated with age, parents which made shorter foraging trips clearly raised chicks which grew faster. Chick survival varied greatly between the 2 seasons (40 versus 97%), which was explained by different levels of nest non-attendance by parents. Chicks in the 2011-2012 season which were exposed to longer periods of non-attendance were particularly vulnerable to unseasonal storms and they were also more vulnerable to kelp gull Larus dominicanus predation while young. In contrast to Cape gannets in the declining west coast populations, chick survival at Bird Island was primarily related to parental protection rather than food provisioning rate, which probably reflects favourable foraging conditions along the southern coast of South Africa. This study highlights the importance of understanding the interplay between factors affecting chick growth and survival for the effective conservation of threatened seabird populations. KEY WORDS: Automated monitoring · Cape gannet · Chick provisioning · Foraging effort · Parental roles · Survival · Time-activity budget · VHF Full text in pdf format PreviousNextCite this article as: Rishworth GM, Pistorius PA (2015) Protection and provisioning: the role of parental behaviour in terms of chick growth and survival in a pelagic seabird. Mar Ecol Prog Ser 530:153-162. https://doi.org/10.3354/meps11317 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 530. Online publication date: June 18, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Short Note: Unusual breeding site for kelp gulls on Deception Island, Antarctica

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Differential reactions to anthropogenic disturbance by two ground-nesting shorebirds

Many ground-nesting shorebirds experience a high level of anthropogenic disturbance, often to the detriment of their breeding success. This study investigated the responses of the Near-Threatened African Black Oystercatcher Haematopus moquini (ABO) and the Least Concern Kelp Gull Larus dominicanus vetula (KG) to anthropogenic disturbance during the pre-breeding and breeding season at three locations differing in levels of anthropogenic disturbance and colony size. Birds were directly approached from over 100 m away and markers were dropped at each behavioural reaction to the approach. Measuring back allowed a quantitative measure of the effects of disturbance. Stand response distances in breeding ABO were location sensitive, which related to disturbance level, showing that they stood up earlier in a highly disturbed location. Neither ambient conditions (wind speed and ambient temperature) nor nesting condition (egg age and clutch size) played a significant role in responses. Interestingly, breeding KG behaviour was affected by location, to a lesser extent by clutch size, but not by ambient conditions. Both ABO and KG significantly altered their behavioural responses to disturbance from pre-breeding to breeding. These results emphasise the need to have a buffer zone surrounding breeding areas excluding human presence to allow for the successful breeding of ABO.

Variation in the Size of Eggs of Kelp Gulls (Larus dominicarius) at Two Colonies in Patagonia, Argentina

Although several studies have reported basic information about the size of Kelp Gull (Larus dominicarius) eggs, no attention has been paid to the comparison of patterns of intra-clutch variation at different breeding sites. Here, the variation in egg size of Kelp Gulls at two colonies from Patagonia, Argentina, was analyzed. The objectives were to characterize egg size variation in Kelp Gulls breeding at a recently established colony in Punta Loma that primarily relies on natural prey; and to evaluate if patterns of intra-clutch variation in that colony differ from those at Vernaci Sudoeste Island, a larger and well-established colony with access to supplementary food in the form of fishery waste. In two-egg clutches, first-eggs were larger than second-eggs. Neither average egg size nor intra-clutch patterns differed between study sites. Also, in two-egg clutches, egg size decreased as date of laying increased, probably due to younger birds laying smaller eggs later in the season. The pattern of intra-clutch variation in three-egg clutches differed between sites. Three-egg clutches at Vernaci Sudoeste Island presented similar sizes for first- and second-eggs and these were larger than third-eggs. This pattern contrasted with the steady decrease in relation to laying order that was observed at Punta Loma. Also, second-and third-eggs from Vernaci Sudoeste Island were larger than corresponding eggs from Punta Loma. Our data suggest that differences in egg size between colonies could be the consequence of enhanced food availability at Vernaci Sudoeste Island in the form of discards generated by trawl fisheries. Future studies to evaluate age of birds and inter-annual environmental stochasticity are needed to elucidate the effect of these factors on egg size variation.

A changing distribution of seabirds in South Africa—the possible impact of climate and its consequences

In the southern Benguela ecosystem off South Africa, there were recent shifts to the south and east in the distributions of three forage resources (anchovy, sardine, rock lobster), which probably were influenced by environmental change although fishing too may have played a part. In this study, we review information on trends in distributions and numbers of eight seabirds breeding in South Africa. For five species that feed predominantly on anchovy, sardine or rock lobster, their populations off northwest South Africa decreased markedly. For three of these species, which exhibit behavioural inertia and have restricted foraging ranges when breeding (African penguin, Cape cormorant, bank cormorant), there were large decreases in their overall populations in South Africa. Conversely, for two showing more plasticity and able to range over wide areas or move between breeding localities (Cape gannet, swift tern) there were increases. It is thought that movement of forage resources away from the northern islands led to a mismatch in the distributions of breeding localities and prey of dependent seabirds off western South Africa and to attempts by several species to establish colonies on the southern mainland closer to food resources. There also were shifts to the south and east in the distributions of three seabirds that do not compete with fisheries for prey (crowned cormorant, white-breasted cormorant, kelp gull), suggesting some environmental forcing, but decreases of these species off northwest South Africa were less severe and populations in South Africa remained stable or increased in the long term. It is likely, because many fishing plants are located in the northwest, that there was increased competition between seabirds and fisheries for prey as forage resources moved south and east. Potential interventions to mitigate the adverse impacts of distributional changes for seabirds include allocations of allowable catches of shared forage resources at regional levels,

Transfer processes drive population dynamics of kelp gull colonies in Patagonia: Implications for management strategies

The dispersal of individuals among breeding sites is considered to be one of the key processes in seabird population dynamics. The kelp gull (Larus dominicanus) is the most abundant gull in coastal Argentina, although its population dynamics in the region remains poorly understood. This article aims to address aspects of kelp gull demography along a wide coastal sector (~1800 km) in northern Patagonia to improve our understanding of population changes and contribute to the design of management strategies and monitoring programmes. Modelled scenarios suggest that annual increases of 10–20% are high for the species, and 29% of 62 evaluated colonies presented growth rates within this high reference range. Transfer processes among colonies (e.g. source–sink) contributed to the growth of at least six kelp gull colonies. These processes have been instrumental in the growth of small, and in some cases recently established colonies, which had generally higher growth rates and were found near large and long-established colonies. These are the first studies of kelp gull demography on the coasts of Argentina aimed at understanding the population dynamics of this species in a metapopulation context.

Pseudo-egg and exotic egg adoption by Kelp Gulls Larus dominicanus vetula

Ground-nesting birds, particularly larids, are known to include a variety of items in their nests as pseudo-eggs, as well as to adopt the eggs of conspecifics or other species. Three hypotheses have been put forward to explain this phenomenon: incubation stimulus, mistaken-food, and mistaken-egg hypotheses. Of 382 Kelp Gull Larus dominicanus vetula nests monitored during 2013/14, 11 instances of pseudo-egg (mostly driftwood and beef/ lamb bones), and one instance of exotic egg, adoption were recorded. A combination of all three hypotheses was attributed for the adoption of pseudo-eggs, whereas the exotic egg adoption could have been due to the need for incubation stimulus or a case of mistaken food.

Конкурентні взаємини птахiв Антарктики в локальному осередку людської дiяльностi (на прикладі УАС «Академiк Вернадський»)

The example of interspecies relationship birds-euryphages Aпtarctic species displayed competition in artificial trophic localities - in the hearth of recycling kitchen waste. ln particular, Kelp Gull (Larus dominicanus), South Polar Skua (Catharacta maccormicki), Pale-faced Sheathbill (Chionis alba) and Southern Giant Petrel (Macronectes giganteus) form а commensal relationship with the employees of the station (useful for birds and indifferent for men). At the same time, between themselves they show the hard rivalry of the trophic resources. Seagulls are the main species of avifauna, which for the year is changing its competitors. From November to April skuas are competitors for the gulls. They have а superiority in the number for February and March. Since the second half of April gulls compete with sheathbills. The gradual disappearance of sheathbills observed in winter - as а consequence of the appearance and aggression of skuas. ln summer, near the station occasionally observed petrels, which in spite of а small synanthropes, monopolize feed.

Whales vs. gulls: Assessing trade-offs in wildlife and waste management in Patagonia, Argentina

In Península Valdés, (Patagonia) Argentina, the consequences of poor waste management and an overpopulation of kelp gulls has led to gulls feeding on living southern right whales, potentially causing losses to the tourism industry through loss in coastal quality and suboptimal right whale viewing experiences. Despite local progress in closing waste disposal sites and culling gulls, both waste and pest problems persist. While this problem could impact the long-term viability of the site as a whale watching destination and present conservation concerns, little research has been done concerning the socio-economic aspects of the problem. The present study interviewed 650 tourists about their willingness to pay to manage the gulls versus the waste in order to reduce the gull population and remove the risk to the whales. This research finds that tourists favor addressing the human-driven component of the problem, the waste, over culling the natural component of the problem, the kelp gulls. These findings present a remarkable insight to assessing trade-offs between two management strategies to a local problem associated with coastal development and tourism. The results could further be broadened to other destinations facing waste and pest management challenges in the face of growing tourism and urbanization.

Change in southern right whale breathing behavior in response to gull attacks

Animals may develop behavioral responses to avoid discomforting situations. In particular, pain can result in learned avoidance behaviors. We report such a case in southern right whales (Eubalaena australis) that have been the target of attacks by kelp gulls (Larus dominicanus) that feed on their skin and blubber in the surrounded waters of Peninsula Valdes, Chubut (Argentina) since the 1980s. The increase in the attacks over the years triggered on whales the development of alternative postures to keep their backs protected from the gulls. Recently, a particular avoidance behavior has been observed, the “oblique breathing,” in which whales breathe with only the head out of the water. The main goal of this work is to describe the emergence of oblique breathing in two areas of Golfo Nuevo (P. Valdes) which have high number of whales and gull attacks, during the whale reproductive seasons in 2010, 2012 and 2013. Results suggest that all age and sex classes of whales can breathe obliquely. Emergence of the oblique breathing seems to have proceeded in three stages: (1) the origin, with rare observations, (2) the spread, when the behavior was registered only during gull attacks and (3) the establishment, when whales performed it in a preventive manner, even when attacks were not occurring. Oblique breathing is likely to pose extra energy costs, which could be detrimental to whales, especially for recently born calves. However, given the increasing prevalence of this behavior, it seems to be a useful strategy to prevent harassment by gulls.

Climate and competition in abundance trends in native and invasive Tasmanian gulls

Climate and competition influence seabird population size yet are rarely considered simultaneously. Here, we consider the influence of climate on nominal abundance trends, and test for evidence of interspecific competition based on 31 yr of count data from 3 co-occurring gull spe- cies in southeastern Tasmania. The silver gull Chroicocephalus novaehollandiae and Pacific gull Larus pacificus are native, while the kelp gull L. dominicanus established in Tasmania from New Zealand in the 1950s. We applied population growth models where either growth rate or carrying capacity was a function of both large-scale climate variables and local conditions. For the kelp gull, a null model without any climate variables was selected, consistent with recent population establishment and increase. For the 2 native species, climate covariates were included, and for both, wind speed was important; for Pacific gulls, the El Nino-Southern Oscillation and regional sea surface temperature were also included in the selected model. These results are consistent with bottom-up forcing in the southeastern Tasmanian marine ecosystem; increased wind forcing leads to increased productivity and higher abundance of an important euphausiid prey species (Nyctiphanes australis). In years with lower wind speeds, warmer waters and higher water column stability, N. australis production is reduced. Models allowing competition effects by the kelp gull on the 2 native species performed poorly relative to models with climate covariates. Thus, compe- tition alone is not a sufficient explanatory factor for observed changes in the 2 native species, and management strategies to maintain populations of the endemic Pacific gull should seek to reduce other stressors, including factors related to climate change.

Kelp Gulls (Larus dominicanus) killed and injured by discarded monofilament lines at a marine recreational fishery in northern Patagonia

Among marine debris, monofilament fishing lines often result in negative impacts on marine organisms. We characterized marine debris and incidence of lost and discarded monofilament lines along beaches used by recreational fishers, and report the impact of lines on Kelp Gulls (Larus dominicanus) at the Bahía San Blas protected area, site of one of the main shore-based recreational fisheries of the southwestern Atlantic. Over 55% of the marine debris recorded originated from recreational fishing activities. Balls of tangled monofilament lines were found at a rate of 40.5 items per km. A total of 27 adult Kelp Gulls were found entangled with monofilament. All individuals were tangled to vegetation within colony boundaries. Four of the gulls had a monofilament line protruding from the bill, showing that they may be also killed when trying to obtain bait. Our results indicate that lost or discarded monofilament lines in the Bahía San Blas recreational fishing area result in undesired impacts on coastal wildlife.

Species-specific population trends detected for penguins, gulls and cormorants over 20 years in sub-Antarctic Fuegian Archipelago

Understanding the dynamics and causes of population trends are essential for seabird conservation. Long-term studies of seabirds at high-latitude (Antarctic, sub-Antarctic and Arctic) regions have shown contrasting species-specific trends in population size in response to climate change and anthropogenic pressures. We have studied for the last 20 years (1992–2012) the population trends of seven seabird species that breed in the Beagle Channel, south-eastern Tierra del Fuego and at Staten Island, a sub-Antarctic region in southern Argentina. The numbers of Magellanic and Gentoo Penguins increased significantly since 1992 (by >15 % year−1). In comparison, the populations of Imperial Cormorants, Dolphin Gulls and Kelp Gulls increased at slower rates (<5 % year−1), while the Rock Cormorant population even decreased by 1.3 % year−1. At Staten Island, the numbers of Rockhopper Penguins decreased by 24 % between the censuses of 1998 and 2010, whereas the population of Magellanic Penguins increased by 227 % during the same period. Over the study period, air and sea-surface temperatures remained stable in our study area, suggesting that the detected population changes are not driven by the climate. This finding contrasts with the detected links between increasing temperature trends and seabird population changes reported from Antarctic and Arctic regions. The level of tourism and size of the permanent human population has increased in the Beagle Channel area during the last 20 years and could be responsible for the increase of gull populations. The seabird species that received the highest number of visitors (Imperial Cormorants and penguin species) seem to be adapted or at least indifferent to pressures exerted by tourism, as their populations increased during the study period. In addition, increasing numbers of seabirds in the area may generally be leading to higher abundances of scavenging species (e.g. gulls).

Demographic and Breeding Performance of a New Kelp GullLarus dominicanusColony in Patagonia, Argentina

Fil: Lisnizer, Nora. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Nacional Patagonico; Argentina

Processes influencing the population dynamics and conservation of African penguins on Dyer Island, South Africa

Dyer Island, South Africa, supported the largest African penguin Spheniscus demersus colony in 1979 (22 655 breeding pairs), but population dynamics of the species have not followed the trends of adjacent colonies in years of high fish abundance or shifts in prey distribution. Less than 1 500 pairs were breeding on Dyer Island in 2013. Available knowledge on demographic parameters was collated and ecological processes were quantified. Juvenile and adult survival probabilities estimated for birds ringed on Dyer Island between 2005 and 2011 were 0.247 (SE 0.06) and 0.545 (SE 0.05) respectively. Juveniles had a high probability (0.918; SE 0.077) of moving away from Dyer Island. Predation by seals and kelp gulls, as well as oiling, are currently important top-down pressures on penguins on Dyer Island. Numbers of birds breeding on the island were negatively correlated with purse-seine catches 20 nautical miles around it. However, it seems that once the colony size is <3 500 breeding pairs, the importance of fishing pressure diminishes, suggesting that once a colony has been reduced to a relatively small size, its growth is limited by pressures other than fishing. From the review of available knowledge presented here, we recommend a number of management options that should be tested in a suitable model.

Reproductive Dynamics of Sterna hirundinacea Lesson, 1831 in Ilha dos Cardos, Santa Catarina, Brazil.

In this work, we intend to describe the reproductive dynamics of Sterna hirundinacea in an island from South Brazil. We studied the reproductive biology of this species in its natural environment and provide data on their growth, survival, and reproductive success in Ilha dos Cardos, Santa Catarina, South Brazil. Samplings were carried out daily on the island throughout the reproductive seasons of 2003, 2005, and 2006 and the different stages of development of the chicks were characterized according to age, length of the beak, and plumage characteristics. We provide a basic equation Lm = 167.91 (1 − e −0.062t−(−0.23)) to determine the approximate age of individuals using their body mass. The main cause of chick mortality on the island was natural (63.17% in 2003, 81.41% in 2005, and 79.96% in 2006), whereas predation contributed to mortality in a proportion of 38.83% in 2003, 18.59% in 2005, and 20.04% in 2006. The absence in the area of the chicks' main predator, Kelp gull (Larus dominicanus), the large number of chicks that reached the final stages of development, and their reproductive success demonstrate that Ilha dos Cardos is an important breeding site for the species in southern Brazil.

Enteric bacteria in Olrog’s Gull (Larus atlanticus) and Kelp Gull (Larus dominicanus) from the Bahía Blanca Estuary, Argentina

The Bahía Blanca Estuary in Argentina is under the effect of chronic microbiological pollution with untreated raw sewage and the pathogens associated with it. In this estuary, there are breeding colonies of Olrog’s Gull (Larus atlanticus) and Kelp Gull (Larus dominicanus), where parents feed chicks and themselves on prey and food items foraged at or near sewage outfalls and refuse tips where they can be exposed to pathogens of human and animal origin. The objective of this study was to assess the role of Olrog’s Gull and Kelp Gull as carriers of zoonotic pathogens of faecal origin. Bacterial recovery from faecal samples of both gull species was positive for Salmonella enterica var. Typhimurium, Salmonella enterica var. Gallinarum, Escherichia coli, Shigella dysenteriae, Enterobacter cloacae and Klebsiella pneumoniae. The prevalence and diversity of pathogens varied between gull species, and Olrog’s Gull tested positive for a wider range of pathogens than Kelp Gull. Escherichia coli was the most prevalent bacteria in chicks and adults of both gull species, followed by Salmonella spp. in Olrog’s Gull chicks, and Enterobacter cloacae and Shigella dysenteriae in Olrog’s Gull adults. The potential use of these gull species as sentinels of microbiological pollution in the Bahía Blanca Estuary is proposed.

Antarctic Site Inventory breeding bird survey data, 1994–2013

AbstractThis data set represents the accumulation of 19 years of seabird population abundance data collected by the Antarctic Site Inventory, an opportunistic vessel‐based monitoring program surveying the Antarctic Peninsula and associated sub‐Antarctic Islands. This Data Paper, which includes 1124 records from 113 locations for seven species of seabirds (Adélie Penguin [Pygoscelis adeliae], Gentoo Penguin [P. papua], Chinstrap Penguin [P. antarctica], Macaroni Penguin [Eudyptes chrysolophus], Blue‐eyed Shag [Phalacrocorax atriceps], Kelp Gull [Larus dominicanus], and Southern Giant Petrel [Macronectes giganteus]), includes data already published by the Antarctic Site Inventory as well as seven years of recent data not previously published. Census data represent a mix of nest and chick counts; each census record includes the location, date, and precision of the census count, along with any auxiliary notes. Included with the database are maps to clarify the location of specific breeding populations that may be new (and thus not previously reported) or ambiguous. This compilation represents the best single source of raw data on the spatiotemporal dynamics of the Pygoscelis penguins in the Antarctic Peninsula region and provides population data on several flying bird species less frequently studied.

Seabird and dolphin associations: do seabirds benefit from feeding in association with dusky dolphins in Patagonia?

The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities seabirds were most commonly associated, and the size of flock in relation to the number of dolphins in a group. Since both seabirds and dolphins may display different feeding strategies, we also investigated if benefits differed among seabird species. Data were collected in Golfo Nuevo (42°20′S65°00′W) on-board a research vessel between 2001 and 2008. A total of 224 mixed groups of seabirds were encountered during this study. The seabird–dolphin associations were mainly observed during dusky dolphin surface feeding. Shearwaters and kelp gulls were mainly observed in flocks that were associated with dolphins, while Magellanic penguins and cormorants were mainly observed without dolphins. Seabirds may be conditioned to the foraging strategy of dolphins, since birds are associated with dolphins only during dolphin surface feeding. This association probably helped seabirds to find prey, but there were no obvious benefits to dolphins.