Breeding ecology of Kittlitz's Murrelets on Kodiak Island, Alaska

Abstract

Little is known about the breeding ecology of Kittlitz's Murrelets (Brachyramphus brevirostris), a species suspected to have experienced both local and regional population declines in recent years. We studied aspects of their breeding ecology on Kodiak Island, Alaska, to better understand this poorly described member of the family Alcidae. We found 53 nests of Kittlitz's Murrelets during our study (2008–2011) and placed nest cameras at 33 nests to collect data on parental nest attendance, nestling provisioning, and nest survival. Incubation shift exchanges by adults generally occurs either prior to sunrise or after sunset. Adults brooded nestlings for just one day after hatching and did not attend nests thereafter except during provisioning visits. Adults provisioned nestlings an average of 107 times during nestling periods, with a single fish delivered during each visit. Pacific sand lance (Ammodytes hexapterus), a high‐lipid forage fish, accounted for 92% of fish delivered to nestlings. Nestlings grew rapidly, with a logistic growth rate constant (K) of 0.291, the highest rate yet documented among semiprecocial alcids. Young fledged an average of 25 d after hatching, when their body mass had reached an asymptote of 135.5 g, or 57% of adult body mass. Age at fledging and asymptotic nestling body mass (percent of adult mass) were low compared to other semiprecocial alcids. The mean number of young fledged per nest was 0.093, with 47% of nests predated, and nestlings dying prior to fledging at 21% of nests. The low number of parental provisioning visits, rapid nestling growth rates, and short nestling periods are consistent with adaptations to reduce the likelihood of nest predation and the energy expended by parents. The risk of nest predation and high energetic cost of breeding may make the reproductive success of Kittlitz's Murrelets more sensitive to declines in the availability and quality of their prey than most other alcids.

Can oceanic prey effects on growth and time to fledging mediate terrestrial predator limitation of an at‐risk seabird?

“…We placed still‐image, motion‐triggered cameras (Reconyx, Holmen, Wisconsin, USA; Primos, PC900 or PC90) 1‒3 m from active nests to monitor nest activity. Experiments showed that camera placement had no detectable effect on nest success (Lawonn et al 2018 b ), and cameras were set on every nest studied starting in 2011 (only every other nest before that). In 2011, three cameras were set to 1‐min intervals; out of 199 meal deliveries recorded, only one visit was shorter than 3 min, indicating a 3‐min interval was adequate to film >99% of visits by parents to the nest (Lawonn et al 2018b).…”

“…Experiments showed that camera placement had no detectable effect on nest success (Lawonn et al 2018 b ), and cameras were set on every nest studied starting in 2011 (only every other nest before that). In 2011, three cameras were set to 1‐min intervals; out of 199 meal deliveries recorded, only one visit was shorter than 3 min, indicating a 3‐min interval was adequate to film >99% of visits by parents to the nest (Lawonn et al 2018b). Thereafter, all nest cameras were set to trigger after detecting animal motion (3 images at 1‐s intervals), as well as at standard 3‐min intervals from discovery of the nest to fledging.…”

“…However, when land‐based predators gain access to nests, predation can become a major limitation on breeding success (Towns et al 2011, Iverson et al 2014). For the Kittlitz’s Murrelet ( Brachyramphus brevirostris ) on western Kodiak Island, Alaska, high rates of nest predation by red foxes ( Vulpes vulpes ) suggest that land‐based predators and not ocean conditions control nest success (Lawonn et al 2018 b ). However, if the quantity or quality of prey delivered to chicks is limited by ocean conditions, reduced growth rates can extend the nestling period and indirectly increase the chicks’ exposure to predators.…”

“…1; Felis et al 2016, Day et al 2017, Lawonn et al 2018 a ). During the 20‒40 d of the nestling period, parents deliver single planktivorous fish to chicks 1‒12 times per day (Kaler et al 2011, Lawonn et al 2018 b ).…”

“…1). Compared to other semi‐precocial alcids (Sealy 1973), Kittlitz’s Murrelet has among the highest growth rates and lowest fractions of adult mass at fledging, and as a result the shortest period between hatching and fledging (Lawonn et al 2018 b ). This strategy presumably offsets the potentially high vulnerability of Kittlitz’s Murrelet nests to predation, by minimizing the duration of exposure to predators (Litzow et al 2002, Romano et al 2006).…”