Terry M. Sullivan

Bio: Terry M. Sullivan is an academic researcher. The author has contributed to research in topics: Population & Larus glaucescens. The author has an hindex of 1, co-authored 1 publications receiving 16 citations.

Population trends of nesting Glaucous-winged Gulls, Larus glaucescens, in the southern Strait of Georgia, British Columbia

Abstract: Between 1986 and 1999, the number of nesting Glaucous-winged Gulls (Larus glaucescens) at fourteen breeding colonies declined by 31% (1610 nests) in the southern Strait of Georgia, British Columbia. Declines in the number of nesting pairs at surveyed colonies ranged between 6% and 81% with the smallest change occurring on the largest breeding colony in the study area. We suggest that Glaucous-winged Gull breeding population declines in the southern Strait of Georgia may be due to increased frequency of colony disturbance, in particular increased disturbance by Bald Eagles (Haliaeetus leucocephalus).

Density-dependence in the survival and reproduction of Bald Eagles: Linkages to Chum Salmon†

Abstract: During the late 20th Century, due to decreases in both contamination and persecution, bald eagle (Haliaeetus leucocephalus) populations increased dramatically. Currently, mechanisms regulating eagle populations are not well understood. To examine potential regulating processes in the Pacific Northwest, where eagles are no longer primarily regulated by contaminants or direct persecution, we examined bald eagle reproductive success, breeding populations, winter populations, mortality, and salmon stream use. Wintering and breeding eagle populations in south-coastal British Columbia (BC) quadrupled between the early 1980s and the late 1990s, and have since stabilized. Density-dependent declines in reproduction occurred during 1986–2009, but not through changes in site quality. Mid-winter survival was crucial as most mortality occurred then, and models showed that density-dependent reductions in population growth rates were partially due to reduced survival. Wintering eagles in British Columbia fed he...

Foraging ecology of bald eagles at an urban landfill

Abstract: We observed Bald Eagles (Haliaeetus leucocephalus) foraging at the landfill in Vancouver, British Columbia, Canada, 1994–1996 and 2001–2002, to determine (1) diet and time budgets of eagles visiting the landfill; (2) whether food taken from the landfill provided a significant energy source for local eagle populations; and (3) the effects of eagle density and weather on eagle behavior. Eagles fed primarily on human refuse (95%, n = 628), but food items taken from the landfill accounted for only 10 ± 3% of their daily energy needs. Subadults foraged at the landfill more often than adults, and most “refuse specialists” appeared to be subadults. Eagle time budgets consisted of mostly resting (91%), the remainder largely spent drinking (2.6%), scavenging (2.3%), and pirating (1.8%). Resting increased with wind speed, and foraging efficiency declined with precipitation, consistent with the hypothesis that the landfill is primarily a location for resting during inclement weather. Foraging efficiency dec...

Unintended consequences: how the recovery of sea eagle Haliaeetus spp. populations in the northern hemisphere is affecting seabirds

Abstract: Adult seabirds experience predation by many species. At sea, they are taken by predatory fish such as white sharks Carcharodon carcharias (Johnson et al. 2006), and by marine mammals including killer whales Orca orcinus (Dahleim & White 2010), true seals (Penny & Lowry 1967, Cobley & Bell 1998), fur-seals and sealions (McHugh 1952, Long & Gilbert 1997, David et al. 2003, Lalas et al. 2007, Charbonnier et al. 2010), walrus Odobenus rosmarus (Mallory et al. 2004), and sea otters Enhydra lutris (Riedman & Estes 1988). On land, they are taken by native and non-native mammals including rodents (Sealy 1982, Blight et al. 2000, Angel et al. 2009) and carnivores ranging in size from shorttailed weasels Mustela erminea (Cairns 1985) to polar bears Ursus maritimus (Donaldson et al. 1995). In addition, many are taken on land by avian predators, including Giant Petrels Macronectes spp. (Emslie et al. 1995), hawks (Lewis 2003), falcons (Beebe 1960, Booms & Fuller 2003), eagles (Zaun 2009), owls (Morse 1971, Hayward et al. 1993, Velarde et al. 2007), rails (Brothers 1984), gulls (Spear 1993), skuas Stercorarius spp. (Muller-Schwarze & Muller-Schwarze 1973), sheathbills Chionis spp. (Jouventin et al. 1996), and passerines (Verbeek 1982, Ryan & Moloney 1991, Gaston & Elliot 1996).

feathers collected in the Pacific Northwest of North America

Abstract: The world's oceans have undergone significant ecological changes following European colonial expansion and associated industrialization. Seabirds are useful indicators of marine food web structure and can be used to track multidecadal environmental change, potentially reflecting long-term human impacts. We used stable isotope (δ(13)C, δ(15)N) analysis of feathers from glaucous-winged gulls (Larus glaucescens) in a heavily disturbed region of the northeast Pacific to ask whether diets of this generalist forager changed in response to shifts in food availability over 150 years, and whether any detected change might explain long-term trends in gull abundance. Sampled feathers came from birds collected between 1860 and 2009 at nesting colonies in the Salish Sea, a transboundary marine system adjacent to Washington, USA and British Columbia, Canada. To determine whether temporal trends in stable isotope ratios might simply reflect changes to baseline environmental values, we also analysed muscle tissue from forage fishes collected in the same region over a multidecadal timeframe. Values of δ(13)C and δ(15)N declined since 1860 in both subadult and adult gulls (δ(13)C, ~ 2-6‰; δ(15)N, ~4-5‰), indicating that their diet has become less marine over time, and that birds now feed at a lower trophic level than previously. Conversely, forage fish δ(13)C and δ(15)N values showed no trends, supporting our conclusion that gull feather values were indicative of declines in marine food availability rather than of baseline environmental change. Gradual declines in feather isotope values are consistent with trends predicted had gulls consumed less fish over time, but were equivocal with respect to whether gulls had switched to a more garbage-based diet, or one comprising marine invertebrates. Nevertheless, our results suggest a long-term decrease in diet quality linked to declining fish abundance or other anthropogenic influences, and may help to explain regional population declines in this species and other piscivores.

Changing gull diet in a changing world: A 150‐year stable isotope (δ13C, δ15N) record from feathers collected in the Pacific Northwest of North America

Abstract: The world's oceans have undergone significant ecological changes following European colonial expansion and associated industrialization. Seabirds are useful indicators of marine food web structure and can be used to track multidecadal environmental change, potentially reflecting long-term human impacts. We used stable isotope (δ(13)C, δ(15)N) analysis of feathers from glaucous-winged gulls (Larus glaucescens) in a heavily disturbed region of the northeast Pacific to ask whether diets of this generalist forager changed in response to shifts in food availability over 150 years, and whether any detected change might explain long-term trends in gull abundance. Sampled feathers came from birds collected between 1860 and 2009 at nesting colonies in the Salish Sea, a transboundary marine system adjacent to Washington, USA and British Columbia, Canada. To determine whether temporal trends in stable isotope ratios might simply reflect changes to baseline environmental values, we also analysed muscle tissue from forage fishes collected in the same region over a multidecadal timeframe. Values of δ(13)C and δ(15)N declined since 1860 in both subadult and adult gulls (δ(13)C, ~ 2-6‰; δ(15)N, ~4-5‰), indicating that their diet has become less marine over time, and that birds now feed at a lower trophic level than previously. Conversely, forage fish δ(13)C and δ(15)N values showed no trends, supporting our conclusion that gull feather values were indicative of declines in marine food availability rather than of baseline environmental change. Gradual declines in feather isotope values are consistent with trends predicted had gulls consumed less fish over time, but were equivocal with respect to whether gulls had switched to a more garbage-based diet, or one comprising marine invertebrates. Nevertheless, our results suggest a long-term decrease in diet quality linked to declining fish abundance or other anthropogenic influences, and may help to explain regional population declines in this species and other piscivores.