Figure 3 - uploaded by Tony Diamond
Content may be subject to copyright.
Number of pairs of Arctic terns at the 4 major Arctic tern colonies in the Gulf of Maine, USA, 1901–2014. Seal Island was restored in 1989. Partial censuses on Seal Island began in 2007; counts are extrapolated totals and may be underestimates, especially after 2009. Censuses on Machias Seal Island are typically performed every 2 years. Adapted from Drury (1973), Allen et al. (2012), and Gulf of Maine Seabird Working Group, unpublished data.
Source publication
Lethal control of wildlife represents an ethical concern for managers, exacerbated by a lack of replicated or controlled data for most taxa or regions. The Gulf of Maine (GOM) has a history of intensive lethal and nonlethal predator control to protect terns (Sterna spp.) from inflated populations of predatory gulls, especially herring (Larus argent...
Context in source publication
Context 1
... in New Brunswick, Canada. Lighthouse keepers shot gulls to prevent contamination of their water supply, incidentally benefitting terns ( Anderson and Devlin 1999). Terns have nested uninterrupted since 1870 on MR and 1873 on MSI ( Kress et al. 1983), and over 90% of the Arctic tern population nested at the 3 colonies in the twentieth century (Fig. 3), illustrating their long-term stability (Drury 1973, Kress 1983. Breeding success declined at all 3 colonies when lethal control of persistent gulls was reduced, including automation of PMI's lighthouse in 1975 (Anderson and Devlin 1999), lax control on MR in the late 1960s (Drury 1973), and cessation of lethal control on MSI in 2000 ...
Similar publications
Predation shapes marine benthic communities and affects prey species population dynamics in tropic and temperate coastal systems. However, information on its magnitude in systematically understudied Arctic coastal habitats is scarce. To test predation effects on the diversity and structure of Arctic benthic communities, we conducted caging experime...
Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynami...
Contemporary climate change is predicted to expose some species to altered predation regimes. Losses of Arctic sea ice are causing polar bears to increasingly forage on colonial seaduck eggs in lieu of ice-based hunting of marine mammals. Although polar bear predation of bird eggs has now been widely documented, it is unclear whether this change in...
We placed wire mesh predator exclosures around the nests of Red-necked Phalaropes Phalaropus lobatus at a tundra site outside of Nome, Alaska, in 2011 and 2012. Exclosures were made of 2.5 cm × 5.1 cm wire mesh and were approximately 0.8 m high, 0.8 m in diameter, with a flat top, and were secured to the ground with three metal stakes. We compared...
Despite the presence of invasive black rats (Rattus rattus), common mynas (Acridotheres tristis), and feral domestic cats (Felis catus), sooty terns (Onychoprion fuscatus) breed in large numbers on Ascension Island in the tropical South Atlantic Ocean. These introduced predators impact the terns by destroying eggs or interrupting incubation (mynas)...
Citations
... During the literature screen, we flagged five relevant review articles (Beauchamp et al., 1996;Franks et al., 2018;Hartway & Mills, 2012;Scopel & Diamond, 2017;Smith et al., 2011) and searched their reference lists for articles not found in the structured literature search. We also searched the reference and citation lists of the papers identified as suitable for our review in Covidence between the 12th and 13th of October 2023. ...
Implementing effective, affordable and ethical conservation management will be crucial for minimising future biodiversity losses. Such management requires reliable foundational evidence to help managers make informed choices about how to address the needs of their target species. Unfortunately, such evidence is still lacking for many species and management scenarios.
One major global challenge is improving the reproductive success of threatened species in the context of predation. We conducted a systematic review and meta‐analysis of in situ experiments that used non‐lethal methods to protect bird nests against predators, with the aims of summarising global trends in nest protection efforts, comparing the effectiveness of different protection measures and informing future research and management. We considered peer‐reviewed studies in English.
We detected a large geographic and taxonomic bias in the evidence base with 58% of articles conducted in North America and 76% on ground‐nesting birds. Less than 3% of articles involved taxa listed as Endangered or Critically Endangered and 51% of study units lasted just a single breeding season.
Nests protected with exclosures, fences and guards were more likely to be successful than their unprotected controls. Interventions involving deterrents, conditioned taste aversion, chemical camouflage and diversionary feeding did not have a significant positive effect on nest success, but the interventions in these categories were less common and more diverse in nature.
Synthesis and applications. To increase their conservation value, future non‐lethal nest protection experiments should whenever possible clearly state overall aims, take place over multiple seasons, use a comparable control and test non‐lethal protection methods independently of lethal predator control. Greater focus is required on under‐studied taxa such as cup‐nesting songbirds and birds in South America, Africa and Asia, and novel protection techniques such as deterrents and chemical camouflage. Practitioners should consider the evidence we synthesise here when deciding whether non‐lethal nest protection approaches are optimal for their study system, to increase conservation success and reduce ethical and financial costs.
... Addling can be highly effective at reducing hatching success of targeted gull species (Blackwell et al. 2000;Engeman et al. 2012), but it does not reduce adult gull numbers on site within that season (Engeman et al. 2012). Alternatively, nests can be destroyed, which can force gulls to relocate to other breeding areas but may also result in birds simply renesting on site (Scopel and Diamond 2017). When dispersal is the highest priority, managers may first turn to nonlethal approaches that rely on disturbance. ...
... When dispersal is the highest priority, managers may first turn to nonlethal approaches that rely on disturbance. Disturbance-based approaches, such as automated distress calls, pyrotechnics, and falconry, have been shown to have mixed success depending on frequency of disturbance and the specific gull species being targeted Soldatini et al. 2008;Scopel and Diamond 2017). Perhaps the greatest limitation of disturbance-based control is the risk of rapid acclimation when these methods are not paired with other lethal approaches (Olijnyk and Brown 1999;Soldatini et al. 2008), which limits overall efficacy. ...
... For instance, previous efforts have found that avicides can facilitate re-establishment of other waterbird colonies at sites previously dominated by gulls (Kress 1983;Belant 1997). However, this approach presents risks to other avian species that cohabitate the treated area, and outcomes may be limited by immigration of gulls from surrounding populations (Oro and Martínez-Abraín 2007;Scopel and Diamond 2017). Methods such as shooting can be used to selectively target individuals within focal colonies and, if control is maintained at a sufficient threshold, can improve tern breeding success (Guillemette and Brousseau 2001). ...
Context Due to the frequent depredation of eggs and chicks by herring gulls (Larus argentatus), numerous approaches to reduce their impact on tern colonies have been tested by wildlife managers. Previous studies have shown that the use of overhead lines presents a promising method to prevent gull nesting in tern colonies, but little work has evaluated if this approach is suitable for excluding both nesting and non-nesting gulls. Aims The goal of this study was to explore the efficacy of a preventative approach, overhead lines, versus a more widely practiced lethal approach, shooting and trapping. Specifically, we aimed to determine if methods differ in their abilities to deter both gull nesting and presence within treatment areas and identify impacts on common tern (Sterna hirundo) nesting within treatment areas. Methods We applied separate management strategies to two common tern colonies. In one colony, we removed herring gulls via shooting followed by trapping and nest removal, and in the other colony, we erected overhead lines with subsequent trapping at nests established in the treatment area. Key results Gulls appeared to adapt quickly to shooting efforts, limiting efficacy and resulting in no significant change in abundance from pre-treatment levels (P = 0.981). However, gull use of both the colony and surrounding brush declined significantly (P < 0.001) following trapping and nest removal. Meanwhile, the number of gulls in the colony area declined from a pre-treatment average of 56 to only six, following the erection of overhead lines (P < 0.001). Although six gull nests were established within the treatment area (overhead lines), they were not replaced once the parents were trapped and nests destroyed. Conclusions Tern nesting appeared to be unaffected by any of the implemented management activities. Our data suggest that overhead lines may present an alternative to lethal control when seeking to minimise the impacts of gulls on tern colonies. Implications The data presented in this manuscript can be used to guide managers in selecting actions to reduce conflict between gulls and breeding common terns. By using data-informed practices, managers can select the method best suited for their specific needs and priorities.
... This species of gull often feeds at a higher trophic level than other gulls (Maynard & Davoren 2020), with some individuals specializing on a diet of seabird eggs or chicks (Stenhouse & Montevecchi 1999, Veitch et al. 2016. This predatory behaviour sometimes leads to lethal control or nest destruction at colonies overseen by wildlife managers (Scopel & Diamond 2017). ...
... We also showed that the presence of failed breeders at the colony is likely not related to foraging opportunities at the colony, but rather to increased pair-bonding with mates and defense of nesting sites, or reduced predation risk by roosting at a known safe location. The continuous presence of failed breeders near their nesting sites in our study also suggests that destruction of gull nests, a common management practice used to protect other seabirds (such as alcids and terns) from gull predation (Scopel & Diamond 2017), may not effectively reduce predation. Exploring tag effects on Great Black-backed Gulls that would otherwise be targeted for nest destruction would provide an opportunity to better understand the causes of breeding failure associated with tagging, and it would provide increased knowledge of gull foraging behaviour and nest site attendance. ...
Territoriality for breeding sites comes at an energetic cost—individuals actively defend the site from competitors and potential predators, thus precluding themselves from self-maintenance (e.g., foraging, preening) or offspring care. Breeding individuals are also constrained to central place foraging within a limited range of the territory. For these reasons, many seabirds do not spend extensive periods or make regular visits to
the colony following breeding failure. To investigate behaviour following breeding failure, we studied colony and nest attendances and daily number of visits for six Great Black-backed Gulls Larus marinus that had failed to breed following global positioning system (GPS) tag attachment on the northeast coast of Newfoundland, Canada. Three failed breeders reduced colony and nest attendance by an average 6.32 h/d (95% confidence
interval [CI]: 1.14) after the estimated date of failure. Conversely, three other failed breeders showed no decrease in attendance, and one individual increased colony attendance by 5.4 h/d. We predicted that failed breeders would be more likely to forage while attending the colony relative to active breeders (i.e., incubating or chick-rearing) due to their lack of offspring and territory to defend. During 18 two-hour nest watches of active and failed breeders, active breeders (n = 4) behaved more aggressively (e.g., predation, swooping) toward gulls at nearby sites in the colony, while failed breeders (n = 6) behaved mostly passively (e.g., preening, sitting, P = 0.029). Our findings indicate that failed breeders continue to attend the colony after breeding failure, indicating potential benefits (e.g., maintaining breeding territory and pair bonding). Our findings also reveal
that using tracking data to indicate breeding failure may be misleading and, thus, we suggest researchers also use visual confirmation of breeding failure, when possible, in future studies. Finally, we warn researchers of the negative effects of tag attachment on gull reproductive success.
... Maccarone 1992, Avery et al. 1995, Peery & Henry 2010, Carle et al. 2017, Ekanayake et al. 2015. Seabirds such as gulls may be fierce nest predators themselves, but some species are also vulnerable to nest predation (Massaro et al. 2001, Kazama 2007, Scopel & Diamond 2017, Mills et al. 2018, including the Lesser Black-backed Gull (Larus fuscus) (Calladine 1997, Bukacinski et al. 1998, Hario 1994, Hallgrimsson & Hersteinsson 2012. ...
Many seabird populations suffer heavily from the destruction of nests by generalist predators. In this study, we analyzed 16 years of data (2005–2020) on the reproductive output of the northern Lesser Black-backed Gull (Larus fuscus fuscus) at Horsvær, the largest assemblage of this subspecies in Norway (up to ca. 400 pairs), in relation to the occurrence of breeding Ravens (Corvus corax). A pair of Ravens were firstly discovered at Horsvær in 2010, and between 2011 and 2016 they were observed with broods (2–5 fledglings) in most years. Between 2017 and 2020, human intervention prevented the Ravens from breeding in the colony. However, in 2020 a pair of Ravens brought their fledglings over from a neighboring island in the middle of the incubation period for the gulls. On average, the nest predation rate was 43% when Ravens had fledglings within the study area. In contrast, only 10% of nests were depredated in years when Ravens did not reproduce successfully or were absent. Moreover, only 0.07 fledglings were on average produced per nest in years when Ravens bred successfully, compared to 0.71 fledglings per nest in years with no Raven reproduction. A high level of nest predation led to a decline in the number of nesting gulls, which was not observed in a neighboring Raven-free colony. Finally, in years with high Raven predation at Horsvær, production of fledglings was still high in yet another nearby Lesser Black-backed Gull colony. The Ravens were established at Horsvær in the absence of people in the spring, and the only option to save these threatened gulls may be to prevent the Ravens from nesting successfully in or near their colonies.
... Gulls provide valuable ecosystem functions (Morris et al. 1992;Sekercioglu 2006) and are popular with bird watchers because of their abundance and many varied plumage characteristics; however, there is often conflict between gulls and human activities and needs. Gulls can negatively impact sensitive wildlife species via competition for space and by predation (Hatch 1970;Becker 1995;Russell and Montevecchi 1996;Pius and Leberg 1997;Scopel and Diamond 2017). In high densities, gulls negatively alter water quality in parts of the Great Lakes and along the Atlantic Coast (Fogarty et al. 2003;Converse et al. 2012;Winton and River 2017). ...
We estimated the allowable annual take of great black-backed gulls Larus marinus, herring gulls L. argentatus, ring-billed gulls L. delawarensis, and laughing gulls Leucophaeus atricilla in the U.S. portion of the Atlantic Flyway to help meet human safety and resource management goals. Gulls can pose a serious threat to aviation, negatively impact other colonial-nesting migratory bird species, and conflict with other human activities. We estimated an annual take limit using a model that incorporated intrinsic population growth rate, minimum population size, and a recovery factor for each species. We estimated intrinsic population growth by combining allometric with life table approaches. We used the recovery factor to restrict the take level of the great black-backed gull beyond that of the other species because of poor data quality and concern about its population status. The herring gull was the only species with comprehensive demographic data. Population sizes used in estimating potential take limit varied greatly among the four species, but estimates of intrinsic population growth rate were similar (range 0.118 to 0.197). The annual potential take limits for the four gull species were 7,963 for herring gulls, 2,081 for great black-backed gulls, 15,039 for laughing gulls, and 14,826 for ring-billed gulls. Comparing average annual take from 2012–2019 to our modeled potential take limit, overharvest has not occurred for great black-backed and laughing gulls, occurred once every 8 y for ring-billed gulls, and occurred over half the time for herring gulls.
... Whenever possible, alternative options to lethal control should be attempted, including egg removal, restricting the access of people to tern colonies to reduce tern disturbance and sensitivity to predators, or limiting the availability of anthropogenic food for the native gulls. Nevertheless, until the population of Yellow-legged Gull returns to more natural levels in the Azores (i.e., pre-1984 populations, before human populations expanded and rubbish dumps became a food source), the lethal control of specific predatory individuals may be necessary for the conservation of Roseate Terns in the Azores, as has been shown in tern colonies in North America (Scopel & Diamond 2017). Monteiro et al. 1998 a The colonization status of potential predators is noted as introduced (int) or native (nat). ...
The Azores Archipelago holds the second most important population of Roseate Terns in the North Atlantic. However, the size of the
population has been decreasing. In this study, we used remote-sensing cameras and visits to the main colonies of Common Terns Sterna
hirundo and Roseate Terns S. dougallii on Terceira Island to identify the causes of breeding failure. Nest depredation by introduced
mammals, particularly rats and cats, was the main cause of breeding failure, leading, in some cases, to the complete destruction of the colony.
Additional threats included nest disturbance by humans and dogs, which caused the destruction of some nests. Measures aimed at mitigating
depredation were tested but in the case of rodents, control plans proved difficult to achieve. This is probably because rodents are widespread
in the Azores, they are not limited by food resources, and/or trapping methods are ineffective.
... Since then, because routine season-long lethal control has not been available whenever necessary, the major factor affecting productivity of the terns has been egg predation by gulls. Scopel & Diamond (2017) showed that throughout the Gulf of Maine seabird colonies, there is a threshold (25%) of egg predation by gulls, above which terns abandon that year's breeding attempts. Accordingly, in the absence of appropriate management of gull predation, tern breeding success cannot be used as an indicator of food supply or other environmental change, and the decline in numbers reflects egg predation by gulls. ...
This paper reviews some of the more obvious changes in the populations and diets of seabirds breeding on Machias Seal Island, at the junction of the Bay of Fundy and the Gulf of Maine, from 1995 through 2015. This is the largest seabird colony in this oceanic ecosystem, hosting colonies of cold-water species at the southern edge of their distribution. My lab's research over 20 years has been focused in two directions-exploring how several closely-related species persist in coexistence here, and interpreting changes in the birds' biology in terms of responses to environmental changes. Diet played a major role in ecological isolation, but has changed considerably in response to virtual disappearance of juvenile herring since the late 1990s and the recent appearance of juvenile haddock. Ocean warming since 2000 has accelerated, especially after a sudden decrease in water temperature and salinity around 2005, which had as much deleterious effect as the subsequent warming. A major finding has been that the three most abundant breeders-Atlantic Puffin, Razorbill, and Arctic Tern-exchange individuals with other colonies in the Gulf of Maine and so each constitutes a true meta-population. This study, with similar collaborative work on those colonies, provides a unique spatial perspective on marine seabird population dynamics in a rapidly-changing ecosystem. Two species (Razorbills and Common Murres) show wholly unexpected increases in numbers, despite declines in several demographic measures that bode ill for the long-term sustainability of this colony.
... Avian species have additionally served as indicators of ecosystem health in conservation and restoration projects worldwide (Weseloh et al. 2002, Frederick et al. 2009, Scopel et al. 2018, Velarde et al. 2019. Despite these values, gulls (Larus spp.) are something of an outlier, often labeled as a "nuisance" to human health and industry (Blokpoel and Tessier 1986, Cleary et al. 2006, Clark et al. 2013, Province of New Brunswick 2013 as well as a threat to other species of conservation (e.g., terns, salmon) and social or economic (e.g., eiders) interest (Donehower and Bird 2008, LaRue 2016, Scopel and Diamond 2017. Nuisance concerns about gulls have caused the focus of wildlife management to shift away from mitigation of human practices that are incompatible with the maintenance of ecological integrity to the control of gulls. ...
Gulls (Larus spp.) are described as generalist, opportunistic feeders that show great flexibility in habitat use. Despite an apparent advantage in changing landscapes, many Larus populations have declined in eastern North America since the 1990s. The main hypothesis explaining gull declines at a broad scale is a decrease in total food availability, especially anthropogenically derived fisheries discards and human refuse as industries and cities have improved their management practices. However, it is difficult to quantify the total proportion of gull diet subsidized by humans to test this hypothesis because many common prey items can be traced to both anthropogenic and nonanthropogenic sources. Our aim was to estimate the proportion of diet derived from anthropogenic food sources for Herring Gull (L. argentatus) during the breeding season at the two largest colonies in the Bay of Fundy, Canada, which are located 36 km apart. GPS loggers were deployed to quantify spatiotemporal movement patterns, and whole blood and feather samples were collected for δ13C and δ15N stable-isotope analysis to estimate diet composition during the incubation and chick-rearing stages of the breeding season. Results indicate that there is spatial segregation in the foraging areas used by gulls from the two colonies. All gulls relied on a variety of anthropogenic food sources, with some individuals selecting heavily on fisheries (i.e., active town wharfs, fish packaging plants, aquaculture pens) and mink (Neovison vison) fur farms. Landfills were not a significant source of food during the breeding season. Our study provides valuable information about the relative reliance of gulls on anthropogenic food subsidies, providing insight into how changing industry practices may affect patterns in nesting and foraging by gulls in the region.
... [Colour figure can be viewed at zslpublications.onlinelibrary.wiley.com.] reduce gull populations (e.g., Blokpoel et al., 1997;Scopel and Diamond, 2017), these measures must be maintained continuously so that its effects can last in time (Thomas, 1972). This is because, as opportunistic species, gulls' generalist feeding behaviour allows them to adapt foraging strategies depending on the type of resources most readily available (Bosch et al., 1994;Duhem et al., 2003Duhem et al., , 2005Egunez et al., 2018). ...
... In fact, while culling served to instantaneously reduce gulls density to practical numbers on the Berlenga, the influence of fertility control along with dumps closure appeared to be critical for the verified local decline. Likewise, other studies show that the effectiveness of animal management actions depends on context-specific environmental conditions (e.g., Scopel and Diamond, 2017;Smith and Carlile, 1993). For instance, the large decrease of the yellow-legged gull population at Dragonera Natural Reserve (Balearic Archipelago, Spain) was attributable to the combined effects of landfill closure and the poisoning of adult birds . ...
... In fact, adult survival is a key factor driving longlived species' population trends (Saether and Bakke, 2000). This explains why variations in the intensity of culling appeared determinant to the yellow-legged gull population trends in both types of scenarios; i.e., culling has a direct effect on adult mortality thus having the potential to dramatically change population trends in the short term (Scopel and Diamond, 2017). Regarding egg destruction effort, it was influential only if fertility control continues during the next 20 years. ...
The yellow‐legged gull (Larus michahellis) is an opportunistic seabird species, whose worldwide demographic increase in the second half of the 20th century was associated to anthropogenic activities, such as the proliferation of open‐air dumps in urban coastal areas. In the small Berlengas archipelago (Peniche, Portugal), the species breeding population reached about 44,000 individuals in 1994, representing a severe ecological pressure in this Biosphere Reserve. In an attempt to control this overpopulation, management actions were implemented in the area, namely, the culling of breeding adults and later egg destruction campaigns. Although the population has been decreasing in recent years, it is unknown how much of this reduction is due to management actions since the closure of open‐air dumps in Portugal might also have influenced the yellow‐legged gull population trends. We developed a dynamic model to test pertinent explanatory hypotheses for this problem, taking into account retrospective population trends under alternative contexts of food availability and management actions. The model was also used to predict population growth patterns under future management scenarios. Our results show that, despite contributing to reduce birds local abundance, egg destruction alone would not be able to trigger the population decrease observed in the last two decades. Instead, the permanent closure of open‐air dumps in 2001 was likely the major driver for the species local decline. In the current context of restricted anthropogenic food sources, our study also suggests that the tendency of the population is to naturally decline. Thus, continuing fertility control campaigns can compromise the future viability of the yellow‐legged gull population on the Berlengas Natural Reserve. Our study highlights the interplay between model‐based research and ecological monitoring to test the effectiveness of ongoing management programmes and to anticipate the ecological consequences of future control of native species.
... Non-specialists, however, may also predate birds and, because they comprise the majority of the breeding population, their overall impact on the prey species may be greater than that of specialist individuals [15]. Incorrect classification of specialists has important empirical repercussions because lethal control of large gulls is strongly advocated to control specialist individuals that predate conservation-important bird species [16,17]. Behavioral metrics that could be used concurrently to improve identification of predatory bird-specialists include: predation outside of a bird's own breeding territory [18,19], use of specialized hunting behaviors [12,20,21], and elongation of breeding territories into feeding territories [12,22] or defense of separate feeding territories [10,14,15]. ...
... Although removing specialist gulls is strongly advocated as a cost-effective management strategy [16,17], opportunistic predation by large gulls cannot be effectively managed using the same techniques. This is because removed individuals would be quickly replaced by conspecifics that require no specialized behavior. ...
Dietary specialization, exploiting a small fraction of available food resources, is commonly reported for gulls and skuas. Predation of birds by these species is usually considered a specialist strategy employed by the minority of the population but non-specialists also predate birds and may actually have a greater impact on the prey species. To date, most studies have focused on predatory bird-specialists, down-playing the possible importance of opportunistic predation by non-specialists. We addressed this by studying diet (regurgitated pellets and prey remains) and behavior of breeding Herring Gulls (Larus argentatus) over three summers at Gull Island, a mixed-species breeding colony in Lake Ontario. One-third of all pellets analyzed contained bird remains, primarily the most numerous breeding bird: Ring-billed Gull (L. delawarensis) chicks (51%) and adults (36%). Although all but one pair of Herring Gulls ate birds, all pairs maintained broad and mostly similar diets, with birds accounting for at most one-third of prey. Behavior also indicated that Herring Gulls at Gull Island were not predatory bird-specialists because predation was too infrequent to meet energetic requirements, was largely unsuccessful and was only ever observed when Ring-billed Gulls strayed into Herring Gull breeding territories. Instead, bird predation appeared mainly opportunistic, increasing with seasonal availability, access to shoreline, proximity to nesting Ring-billed Gulls and breeding territory size. Compared with predatory specialist Herring Gulls in the same region, individuals that predated birds at Gull Island did not display specialist behaviors and killed six times fewer birds (0.1–0.4 per day, on average) but were over 20 times more numerous (98% of the population versus 4%). Thus, our results indicate that opportunistic predation by non-specialists may have important consequences for prey species. Since opportunistic predation cannot be effectively managed using techniques widely advocated for specialist predators, it is essential to investigate cause of predation by large gulls prior to lethal management.
