Aleutian seabirds

Subadult seabirds ‘prospect,’ or visit breeding colonies to evaluate reproductive success, identify suitable habitats, and assess potential partners; however, prospector biology is poorly understood. I explored prospector biology to understand post-natal seabird dispersal and recruitment decisions using Least (Aethia pusilla) and Crested Auklets (A. cristatella). I documented auklet colony attendance, behaviour, and reproductive success and used this foundation to examine the timing of colony attendance by prospecting subadult auklets. Subadult auklets were found to spend much less time socializing than expected and their attendance at the colony appeared to be independent of reproductive success as it was restricted to the incubation period. This study is the first to document differences in adult and subadult behaviour of auklets and attempt to understand patterns of subadult colony attendance and serves as a significant first step towards understanding patterns of subadult recruitment.

My fieldwork was conducted at Gareloi Island, Alaska, USA (51°47'N, 178°47'W), auklets’ prototypical breeding island, hosting some of the largest breeding numbers of Crested Auklets (> 500,000 pairs) anywhere in the Aleutian Islands and perhaps Alaska (Murie 1959, Sowls et al. 1978, Jones & Hart 2006, Major et al. 2017). Gareloi Island is located close to (23 km) a productive shallow pass between Unalga and Kavalga Islands that upwells zooplankton prey (Hunt et al. 1998). Crested Auklets are widespread on this island, nesting at inland sites (lava flows), beach boulders, and associated eroding coastal cliffs (Sowls et al. 1978; Paragi 1996a, 1996b; Jones & Hart 2006; Major et al. 2017). The southeast colony corresponds closely to c. 80 ha of the most recent lava flows and craters from 1930s era volcanic eruptions (Coats 1959, Fig. 2 in Jones & Hart 2006). Jones & Hart (2006) surveyed this site and estimated that the southeast colony supported about 230,175 pairs of Least and Crested Auklets in 2006, with about half believed to be Crested Auklets. For the present research, we selected two high density study plots, ‘Plot D’ (51°45'14.4"N, 178°45'31.9" W) and ‘Tick Mountain’ (51°45'14.1"N, 178°45'27.0"W), located about 300 m inland at an elevation of 40 m a.s.l., close to the geographic center of the southeast colony.

Crested Auklet colony attendance

Seabird colony attendance during their breeding seasons is driven by reproductive obligations of incubation and chick rearing, resulting in relatively predictable attendance patterns near breeding sites. Less is understood about patterns and function of activity ashore at colony sites outside the breeding season. We attempted to quantify year-round activity of crevice-nesting Crested Auklets (Aethia cristatella) at Gareloi Island, Alaska, site of some of their largest colonies. In June and July 2013 and 2014, 94 Crested Auklets (92 adults and 2 subadults) were fitted with uniquely coded 1.0 g VHF radio-tags (0.6% of body mass) at two inland study plots in the southeast colony. Radio receiver-loggers remotely detected and recorded individuals present on the nearby colony site surface 24 h/day from date of tagging through autumn, winter, spring and summer 2013 – 2015. Notably, we found Crested Auklets present in all months of the year, with half of our radio-tagged auklets (n = 47, 29 females, 10 males, 8 unknown sex) detected inland at the colony site during non-breeding months (September – March). Visit duration for these individuals comprised about 0.4% of their total annual colony site activity, this is the first evidence of year-round Crested Auklet colony attendance that may be unique to Gareloi. Other findings included extreme individual variability and intersexual differences in colony attendance frequency, differences in attendance between breeding and non-breeding birds, a lapse in surface activity prior to laying in May, and frequent nocturnal activity on the colony surface. Enhanced circannual patterns of Crested Auklet colony attendance at this island may relate to defense of nesting site and other social advantages, permitted by a nearby highly productive sea area with year-round foraging opportunities.

Wails, C. N., H. L. Major, and I. L. Jones. 2020. Patterns of year-round colony attendance by VHF radio-tagged Crested Auklets (Aethia cristatella) at their prototypical Aleutian breeding site. The Wilson Journal of Ornithology 132 (2): 327–342. doi: 10.1676/1559-4491-132.2.327

Auklet prospecting behavior

Prebreeding, subadult seabirds have been documented prospecting or visiting multiple sites throughout the breeding season to gather information on colony reproductive success, identify suitable habitat, evaluate prey abundance, and locate potential partners; however, many aspects of prospector biology remain unknown. We explored prospector behaviour as a means of furthering our understanding of postnatal seabird dispersal and colony attendance using Least Auklets (Aethia pusilla (Pallas, 1811)) and Crested Auklets (Aethia cristatella (Pallas, 1769)) breeding at Gareloi Island, Alaska, in 2014 and 2015. We recorded age class, length of time spent on the colony, and behaviour for individuals attending a study plot over the course of two breeding seasons. Although prospectors typically spent more time on the colony surface than adults, prospectors rarely socialized with conspecifics during their visits to the colony, possibly due to the absence of a citrus-like feather odour used in olfactory communication. Additionally, we found substantial differences between observed and predicted data between years, demonstrating that other factors (likely prey abundance or quality) influenced behaviour in 2015. Our results suggest that the collective knowledge of seabird prospecting behaviour is not necessarily transferable between taxa and there may be a range of strategies employed by prospectors when assessing colonies.

Wails, C. N. and H. L. Major. 2017. Fitting in with the crowd: the role of prospecting in seabird behavioural trends. Canadian Journal of Zoology 95(4):247-257. doi: 10.1139/cjz-2016-0166

Fluorescent auklet ornaments

We examined the fluorescence of ornaments among three auklet species: Least Auklets (Aethia pusilla), Crested Auklets (Aethia cristatella), and Parakeet Auklets (Aethia psittacula) on Gareloi Island, Alaska during the 2015 breeding season. We found that the ornamental bill plates of Crested Auklets fluoresced, but bill ornaments of Least Auklets and bills of Parakeet Auklets did not. We also found that none of the feathers in these three species exhibited fluorescence. We suggest that differences in ornamentation and fluorescence may be related to life-history strategies associated with sexual selection and predator avoidance.

Wails, C. N., E. D. Gruber, E. Slattery, L. Smith, and H. L. Major. Glowing in the light: fluorescence of bill plates in the Crested Auklet (Aethia cristatella). The Wilson Journal of Ornithology 129(1):155-158. doi: 10.1676/1559-4491-129.1.155

References

Coats 1959 in Investigations of Alaskan volcanoes
Hunt et al 1998 Mar Ecol Prog Ser 167:241-259
Jones & Hart 2006 A survey of inland Least and Crested Auklets breeding colonies at Gareloi Island in the Delarof Islands, Aleutian Islands, Alaska during 2006
Major et al. 2017 J Wildl Manag 81:112-121
Murie 1959 Fauna of the Aleutian Islands and Alaska Peninsula
Paragi 1996a Index counts of Least and Crested Auklets on Gareloi Island, Alaska
Paragi 1996b Eradication of Arctic foxes in 1996 on Gareloi Island, Alaska
Sowls 1978 Catalogue of Alaskan seabird colonies