Polar Biol DOI 10.1007/s00300-015-1651-x ORIGINAL PAPER A comprehensive coastal seabird survey maps out the front lines of ecological change on the western Antarctic Peninsula Paula Casanovas · Ron Naveen · Steve Forrest · Jérôme Poncet · Heather J. Lynch Received: 16 October 2014 / Revised: 14 January 2015 / Accepted: 25 January 2015 © Springer-Verlag Berlin Heidelberg 2015 Abstract Seabirds along the western Antarctic Peninsula different ocean dynamics than in areas just outside Mar- are known to be shifting in abundance and distribution in guerite Bay, has maintained persistent phytoplankton response to changing sea ice and prey distributions, but the blooms over the past decade even as summer sea ice extent, spatial extent of these changes has remained an open which can inhibit access to breeding areas, has declined. question because survey efforts have focused on the more This provides further support for the hypothesis that ocean easily accessed northern coastline. We used a yacht-based productivity and sea ice dynamics are critical factors reg- field expedition (January 5–21, 2013) to complete the first ulating Ade´lie penguin abundance in the region and that comprehensive penguin (Pygoscelis spp.) and blue-eyed Marguerite Bay is now at the front lines of ecological shag (Phalacrocorax [atriceps] bransfieldensis) population change in this region. survey of the Graham and Loubet Coasts of the western Antarctic Peninsula since the mid-1980s. Our surveys Keywords Penguins · Blue-eyed shag · Marguerite document a sharp transition zone at the northern boundary Bay · Sea ice · Phytoplankton blooms of Marguerite Bay; north of this boundary zone, we con- firm widespread declines in Ade´lie penguins and increasing populations of gentoo penguins, but south of this zone we Introduction find Ade´lie populations that have remained stable or increased in abundance since the previous surveys by It is now well established that penguin populations on the Poncet and Poncet (Br Antarct Surv Bull 77:109–129, Antarctic Peninsula have been changing over the past three 1987). Marguerite Bay has long been known as a predator decades (Trivelpiece et al. 2011; Lynch et al. 2012; “hotspot,” but our findings suggest that Marguerite Bay has Ducklow et al. 2013). Particular attention has focused on actually been improving for marine predators for at least widespread declines in the abundance of Ade´lie penguin several decades. Marguerite Bay, which has fundamentally (Pygoscelis adeliae) colonies situated along the western coast of the Antarctic Peninsula (Lynch et al. 2012; Lynch Electronic supplementary material The online version of this and LaRue 2014), as well as increasing abundance and article (doi:10.1007/s00300-015-1651-x) contains supplementary southward expansion of gentoo penguins (P. papua) (Lynch material, which is available to authorized users. et al. 2012). Evidence suggests that environmental factors P. Casanovas · R. Naveen · S. Forrest associated with climate change, such as declining sea ice Oceanites, Inc., Chevy Chase, MD, USA and shifts in primary productivity, play a significant role in these shifting patterns of abundance and distribution (Fra- J. Poncet Golden Fleece Expedition Cruises, Beaver Island, ser et al. 1992; Smith et al. 1999; Croxall et al. 2002; Falkland Islands Clarke et al. 2007; Murphy et al. 2007; Trivelpiece et al. 2011). Most studies to date, however, have focused on & H. J. Lynch ( ) colonies north of 65°S, and thus information on population Ecology and Evolution Department, Stony Brook University, ° Stony Brook, NY 11794, USA changes south of 65 S and in the vicinity of Marguerite e-mail: [email protected] Bay has been limited. The survey work reported by Poncet 123 Polar Biol and Poncet (1987), who censused penguin colonies in this locations due to dispersal of individuals over small island region from 1983 to 1987, is the only comprehensive field archipelagos or islands separated from the mainland. Ide- survey of the region prior to that reported here. Their data ally, each “site” encompasses a single breeding population, provide the baseline against which we can assess changes but we have defined their boundaries and naming schema in the abundance and distribution of penguins breeding to remain consistent with historical precedent. Mild south of 65°S on the western Antarctic Peninsula (WAP). weather conditions and the absence of pack ice facilitated Monitoring seabird populations in the Antarctic is the work, allowing for surveying every day and access to important because changes in their abundance and distri- all targeted sites. We surveyed all of the known breeding bution may indicate regional climate change (Croxall et al. locations described in Poncet and Poncet (1987) south of 2002) or direct or indirect human disturbance (e.g., tour- Moot Point except for Rhyolite Island (69°40′S, 68°47′W), ism, marine traffic, commercial harvesting of marine which could not be reached because of time/ice constraints resources). However, limited data south of 65°S have made and distance. The survey occurred after the peak of pen- it impossible to know whether observed changes persist guin egg-laying (for nest counts) and before the peak of south of the latitudinal range for which data have been penguin chick-cre´ching (for chick counts). We mapped, available. Lynch et al. (2012) found that while Ade´lie through waypoints and tracklogs as appropriate, all sur- penguins were declining over most of the western Antarctic veyed sites, as well as the Golden Fleece’s route. Peninsula (WAP), populations at Bongrain Point, Pourquoi We systematically searched all known or discovered Pas Island (−67.72°, −67.73°) and Red Rock Ridge islands, islets, and penguin/shag colonies thereon, relying (–68.29°, −67.18°) were actually increasing. At the same upon Capt. Je´roˆme Poncet’s [30 years experience navi- time, gentoo penguins were found to be expanding their gating these waters and on his navigation notes from the range further south, prompting Lynch et al. (2012)to surveys described in Poncet and Poncet (1987). With the predict further expansion south to the Berthelot Islands. exception of the shag survey at Green Island, all of our More recent evidence suggests that chinstrap penguins (P. surveys were accomplished by researchers (PC, RN, and antarctica), which are declining regionally (e.g., Lynch SF) on land, proceeding from Golden Fleece to shore by et al. 2012), may also be establishing new colonies at their zodiac. All encountered colonies of gentoo penguins, southern range margin (~65°S), although only in areas chinstrap penguins, Ade´lie penguins, and blue-eyed shags already occupied by other pygoscelid penguins (Lynch were mapped and censused by direct enumeration of et al. 2013). To address these open questions, we organized individual occupied nests or chicks [see Lynch et al. (2008) a multipronged survey of the Graham and Loubet Coasts for details on survey methodology]. We counted nests or (between 65° and 68° South, including the Marguerite Bay chicks individually three times and report the average of area) using a comprehensive yacht-based field survey of those three counts; estimates of abundance are, except as the region supported by a coastal survey of high-resolution noted, accurate to ±5 %. We focused our survey on pen- satellite imagery. While most of the WAP is being moni- guin breeding sites reported by Poncet and Poncet (1987) tored regularly (Lynch et al. 2013), the area south of 65°S and the Wildlife Awareness Manual (Harris 2006), as well is not routinely visited by passenger vessels. Small yacht as at locations that had been determined by remotely operations allow for the surveying of areas that are extre- sensed data to potentially contain rookeries. mely difficult or impossible to reach by bigger vessels and Gentoo penguins were counted at eight census sites. All provide greater flexibility for scheduling travel among gentoo penguins were past the peak of egg-laying, many sites. brooding 1–2 week old chicks, and no cre´ching was observed. In this circumstance, the focus throughout was on obtaining nest counts. Chinstrap penguins were cens- Methods used at seven locations and found breeding in small numbers. Only nests with eggs or 1–2 week old chicks Field survey were observed, and thus, the focus was nest counts. Ade´lie penguins were censused at 31 census sites. Ade´lies were From January 5 to 21, 2013, we used the yacht Golden past the peak of egg-laying, with many chicks already Fleece (with a 19.5 m steel hull, a beam of 6.19 m, and a hatched (mostly 2–4 weeks of age) but not yet starting to maximum draft of 2.48 m) to survey the WAP coastline cre`che, so we focused on nest counts. However, at five sites between 65°06′ and 68°18′S, including offshore islands in in Marguerite Bay (Red Rock Ridge, Lagotellerie Island, the Grandidier Channel, Crystal Sound, the west and Avian Island, Chatos Island, and Cone Island), a significant southern coast of Adelaide Island, and the islands in proportion of the colony had cre´ched and we counted Marguerite Bay (Fig. 1). Over this period, we completed 43 chicks instead of occupied nests. Where it was possible to site censuses, where some sites included multiple census do so, both occupied nests and chicks were simultaneously 123 Polar Biol Fig. 1 Track of the Golden 180o W Fleece route representing the o 60 o S o area searched and surveyed for 30 W 30 W this study. Areas along this track not reported in this paper represent true absence within 70 o S o the detection limits of the 60 W 60o W survey (up to 5 km). a Gerlache Strait area, b Lemaire Channel 80 o S to Green Island area, c Renaud Island area, d Crystal Sound area, e Marguerite Bay area.