Oceanographic and climatic factors influencing breeding and colony attendance patterns of Humboldt penguins Spheniscus humboldti in central Chile

Abstract

A colony of Humboldt penguins Spheniscus humboldti in central Chile was monitored from August 1995 to July 2000 to determine patterns of breeding and colony attendance and how these were affected by climatic (rainfall) and oceanographic (El Niño) factors. Nests were periodically checked for contents and roosting birds were counted from vantage points. Two main breeding events were observed: between August and January (spring event) and between April and June (autumn event). Whereas the spring event regularly produced offspring, the autumn event was systematically affected by rains, causing considerable nest desertion. Adults were present in the colony from August to May, abandoning the colony during winter after the nests were flooded. Juveniles occurred only between November and March. Adults moulted mainly in February, while juveniles moulted in January. During the 1997/98 El Niño episode, the number of breeding pairs was 55 to 85% lower than the mean, the onset of nesting was delayed, and abnormally heavy rainfall flooded nests. While the number of breeding pairs was significantly related to sea surface temperature anomalies (SSTA), breeding success was not. The attendance of adults and juveniles at the colony during El Niño was 25 and 73% lower, respectively, than the mean attendance. This 2-peak breeding strategy of Humboldt penguins appears to have evolved in response to the more favourable oceanographic and climatic conditions of Perú, where breeding is continuous and not interrupted by rains. Although less productive, the species probably maintains its autumnal breeding in central Chile because this provides additional offspring to supplement those regularly produced during the spring event.KEY WORDS: Humboldt penguin · Spheniscus humboldti · El Niño · Nest desertion · Breeding · Colony attendance Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 227: [43][44][45][46][47][48][49][50] 2002 with the tropics where little, if any, seasonal environmental fluctuation occurs and bird breeding may extend over a longer period (Lack 1954, 1967, Furness & Monaghan 1987. Nearly all marine birds follow this synchrous breeding strategy (Lack 1967).The Humboldt penguin Spheniscus humboldti breeds over 4500 km along the Pacific coast of Perú and Chile between 5°and 42°S (Williams 1995). Over this extensive distribution area the species faces considerable latitudinal gradients in oceanographic and climatic factors, including marine productivity, El Niño events, sea surface temperatures and rainfall (see Hunt & Schneider 1987). This situation is likely to expose the species to differential selective pressures over its breeding range.In their northernmost breeding areas along the subtropical Peruvian coast, Humboldt penguins nest throughout the year with well-defined breeding events in autumn and spring (Murphy 1936, Zavalaga & Paredes 1997. Whereas adults remain permanently near the colonies, juveniles are absent for several months after fledging (Zavalaga & Pared...

Evidence for gene flow differs from observed dispersal patterns in the Humboldt penguin, Spheniscus humboldti

“…Useful CMR data for Humboldt penguins is difficult to obtain for several reasons: (1) Their breeding range is prohibitively large along the major axis of the species range; (2) many breeding colonies are difficult to access, or completely inaccessible to researchers (i.e., Paredes et al 2003); (3) reproduction is not predictable and strongly influenced by El Niño events (Araya and Todd 1988;Zavalaga and Paredes 1997;Simeone et al 2002), and; (4) surveys to date are not standardized (Araya et al 2000). Furthermore, dispersal of juvenile Humboldt penguins has not been studied until recently (Simeone et al 2006) and therefore, only very limited data is available.…”

Impacts of climate variation and potential effects of climate change on South American seabirds – a review

“…Valle et al 1987). In central Chile, 55Á85% fewer breeding pairs of Humboldt penguins were present at the breeding colonies during the 1997/98 El Niñ o episode, the onset of nesting was delayed, and abnormally heavy rainfall flooded nests (Simeone et al 2002). While the number of breeding pairs was significantly related to sea surface temperature anomalies (SSTA), breeding success was not.…”

Seasonal variations in the behavioural thermoregulation of roosting Humboldt penguins (Spheniscus humboldti) in north-central Chile

“…80% of the body's insulation in Humboldt penguins (Drent and Stonehouse 1971). During summer, birds have old feathers that will be replaced during the moult in February (Simeone et al 2002). At this stage, feathers probably do not have all their insulative properties (Lustick 1984;Davenport 1992) and birds may require other mechanisms to compensate for this deficiency (e.g.…”

“…In its north and central range, birds breed twice a year with well-defined events in winter and summer, when climatic conditions are most extreme (Paredes et al 2002;Simeone et al 2002). We hypothesise that these conditions are likely to expose penguins to different thermal environments and thus generate differential behavioural responses to balance the birds' thermoregulatory demands.…”