provided by EG-BAMM, Alexander E. Thornton & Andres Barbosa
First described by Johan Reinhold Forster (1781), chinstrap penguins are an ice-intolerant species. They are one of the most easily recognisable penguin species, named for a distinctive, thin band of black feathers that runs across their chin, appearing as a chinstrap connecting black feathers across the crown of their skull and back against an otherwise white body. The penguin phylogenetic tree finds pygoscelid (“brush-tailed”) species branching off from a common ancestor of extant penguins anywhere between 20 and 38 million years ago, with chinstrap penguins diversifying from Adélies several million years later.
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Chinstrap penguins are found solely in marine environments with light pack ice coverage and breed primarily at sites along the Scotia Arc (South Shetlands, South Orkneys, and South Sandwich Islands) and the Antarctic Peninsula reaching around 64°S (BirdLife International 2012, Trivelpiece & Trivelpiece 2013).They may also be found in smaller breeding colonies at other locations, such as South Georgia. During the non-breeding season, birds have been tracked using data-loggers as having a migration range of up to 3,600 kilometres away from the colony site, and have been observed as far south as the northern Ross Sea and even as far north as New Zealand (Trivelpiece & Trivelpiece 2013). Their distribution is currently at risk due to the impacts of global climate change, increased human activity in the region (both tourism and scientific operations), availability of prey, and, amongst other factors, natural primary physical oceanographic processes like the El Niño-Southern Oscillation or Southern Annual Mode (Forcada & Trathan 2009, Barbosa et al. 2012, Trivelpiece & Trivelpiece 2013). In particular, the West Antarctic Peninsula has undergone rapid warming in the past half century, particularly at northern latitudes. As a result, the range of the chinstrap penguin has declined in northern regions and expanded to the south (Forcada & Trathan 2009). With the increased loss of sea ice, it is possible that ice-intolerant chinstrap penguins may be able to take advantage of new chick-rearing habitats as the terrestrial environment continues to thaw, however populations have been found to be declining due to increased competition with active krill fisheries likely through winter mortality (Barbosa et al. 2012, Trivelpiece & Trivelpiece 2013). In addition, with more temperate temperatures and easier passage for vessels, tourists may visit sites further south with increasing frequency, thereby potentially exposing seabirds and other native species to foreign pathogens (Barbosa & Palacios 2009).
The vast majority of the dives of chinstrap are to depths less than 40m - the depth at which krill are found at night - and just under half of these dives were in the epipelagic zone, reaching no more than 5 to 10m (Lishman & Croxall 1983, Kokubun et al. 2010). At night, this species appears to travel out to the shelf-break on longer trips, where they may also consume higher amounts of myctophiids and other small, pelagic fish than they would during the day, when the penguins stay closer to shore (Takahashi et al. 2003, Trivelpiece & Trivelpiece 2013). However, they have been observed diving to depths of approximately 100m (Takahashi et al. 2003) where they may be simply exploring for prey or feeding on krill or benthic organisms (Lishman & Croxall 1983). While traveling, they will porpoise at the surface.
Chinstrap display very slight sexual dimorphism favouring males, but sex can only be definitively determined using complex discriminant analyses based on morphometrics. Their average lifespan is between 16 and 20 years (Trivelpiece & Trivelpiece 2013). The primary predators of chinstrap chicks are the brown skuas (Catharacta antarctica lönnbergi), south polar skuas (C. maccormicki), and giant petrels (Macronectes giganteus) (Trivelpiece & Trivelpiece 2013). As adults chinstrap penguins are the prey of leopard seals (Hydrurga leptonyx) and killer whales (Orcinus orca) (Trivelpiece & Trivelpiece 2013, Pitman & Durban 2010).
Diseases and Parasites: A review of the parasites and pathogens present in chinstrap penguins can be found in Barbosa & Palacios (2009). The presence of several gastrointestinal parasites, such as nematodes (Stegophorus macronectes) or cestodes (Parorchites zederi, Tetrabothrius pauliani) and other accidental parasites as Corynosoma sp. have been recorded in this species. These helminth parasites have been estimated to reduce the body mass of chicks by 6%. Ticks, which also pose health risks to penguins, are also found close to the nests. No intestinal protozoa parasites, such as Cryptosporidium sp. or Giardia sp. have been found in chinstraps, although coccidian (Eimeria pygosceli, Isospora sp. and Sacorcystis sp.) are usually found. Furthermore, some bacteria have been identified, including Staphylococcus sp., Streptococcus sp. or Pseudomonas sp., as well as antibodies for influenza A.
While breeding, chinstrap prefer to establish their colonies on rocky outcrops along sloping swaths of coastline, where they construct nests out of stones (Moreno et al. 1995).
Chinstrap penguins are a charismatic species, known for garrulous, screeching vocalisations (Bustamante & Márquez 1996) and normal pygoscelid behaviours, such as stealing rocks from the nests of their neighbours during courtship to prove fitness (Moreno et al. 1995) or when chicks actively chase parents around a colony before feedings (Bustamante et al. 1992).
The major prey of chinstrap penguins is Antarctic krill (Euphausia superba), for which the species is considered a primary consumer, though their diet may also be supplemented with pelagic fish or benthic organisms such as small crustaceans (Trivelpiece & Trivelpiece 2013, Polito et al. 2011). It has been shown that chinstrap could detect krill by means of olfaction (Amo et al. 2013). On the foraging trips, chinstrap penguins go out to sea for up to 24 hours, whereupon they will make a series of small, undulating dives to catch prey (Trivelpiece & Trivelpiece 2013, Takahashi et al. 2004).
Chinstrap penguins are sexually mature by the time they reach 3-5 years of age, at which point they will navigate their way to a breeding colony in early October through December (Trivelpiece & Trivelpiece 2013). It is suspected that chinstrap penguins have limited natal philopatry (Korczak-Abshire et al. 2012), though site fidelity is high for both males and females once they have bred at a site (Trivelpiece & Trivelpiece 1990).
At breeding sites, chinstraps may often be found co-nesting amongst other closely-related Adélie or gentoo penguins. More often than not, there will still be self-imposed segregation between the species, who nest in sub-colonies of their conspecifics (5-1000 birds), within the larger colony of potentially tens of thousands of birds (Barbosa et al. 1997).
First-time breeders will court a mate while surviving pairs will reunite approximately 82% of the time (Trivelpiece & Trivelpiece 1990) before building a nest made from stones collected from around the breeding colony or from other nests (Moreno et al. 1995). The female lays two eggs, the first of which will be larger, before the pair take turns incubating their eggs for 30-40 days (Trivelpiece & Trivelpiece 2013).
Once an egg hatches, chinstrap parents will rear the chick for 20 to 30 days (typically from January through mid-February) before crèching, which takes another 30 days (end of February). During crèching - which may help to reduce predation of chicks - breeding pairs with two chicks are known to run away from their offspring, who will actively chase them; it has been suggested that this ensures that either the hungrier or stronger of two chicks gets primary access to food (Bustamante et al. 1992).
Immediately following their breeding season, chinstrap penguins will spend up to a month foraging and gaining as much weight as possible before coming back to shore (mid-March through mid-April) to moult their entire plumage (Trivelpiece & Trivelpiece 2013). During moult, birds may lose up to 40% of their body weight (Trivelpiece & Trivelpiece 2013). This is quite significant given that chinstraps have a diminished physiological capacity to cope with fasting (Alonso-Alvarez et al. 2003).
Chinstraps' breeding success ranges 0.60 - 1.80. Mean adult survival and generation time are unknown (Forcada & Trathan 2009). Large breeding groups of chinstraps increase their breeding success, i.e. earlier hatching time and greater chicks survival at fledging (Barbosa et al. 1997). It is not known whether this may be due to increased risk of predation along the peripheral nests, a factor of age (younger birds nesting peripherally) or something else (Barbosa et al. 1997, Moreno et al. 1997). In some cases, good quality nests are able to withstand storms and subsequent flooding better than smaller ones leading to higher breeding success for these nests (e.g. Moreno et al. 1995). Late breeders may also have poorer immune responses than earlier breeders, which may explain their lesser success rates (Moreno et al. 1998).
Climate variations resulting in warmer temperatures have caused pygoscelid species to clutch earlier. When chinstraps and Adélies co-mingle at breeding sites, chinstraps may steal not just stones but the entire nest, thereby causing a decrease in reproductive success of Adélies (Trivelpiece & Volkman 1979). Chinstraps may also out-compete Adélies in foraging in years with low prey availability (Lynnes et al. 2002).
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