Evaluating the breeding phenology of the endangered ‘a‘o (Newell’s Shearwater Puffinus newelli) on Kaua‘i to better focus conservation actions and management decisions

Abstract

Summary The ‘a‘o, or Newell’s Shearwater Puffinus newelli, is an endangered shearwater species endemic to the Hawaiian Islands, with 90% of the world population found on Kaua‘i. Understanding the breeding phenology of the species is vital for identifying key periods for colony management actions and the timing and exposure frequency to infrastructure threats such as powerline collisions and light attraction. We used a combination of direct burrow monitoring and remote cameras at multiple colonies between 2012 and 2019 for a detailed assessment of the breeding phenology for this species. Breeding adults started arriving at the burrow in mid-April, some (but not all) underwent a two-week exodus in May and returned at the end of May to commence incubation. Incubation continued until mid-July. The chick-rearing period ran until the end of September. Fledging peaked in October with the last birds fledging towards the middle of November. Breeding was not synchronised, with a 59-day gap between the first and last fledging birds. The importance of this information to management actions is discussed, particularly in terms of directing management actions to key periods of vulnerability to introduced predators (such as peak incubation, chick emergence, and exercising prior to fledging), the precise timing of fledgling fallout related to light attraction, and directing colony-monitoring actions and translocation projects. We also consider the utility of the data in assessing species composition of powerline collisions and collision risk. Future work using acoustic monitoring is recommended for assessing the phenology of non-breeders and prospectors at colonies.

Small tube-nosed seabirds fledge on the full moon and throughout the lunar cycle

“…Further, adults tend to be less active at the colony during the full moon [12][13][14][15][16]. Together, these results suggest that nocturnal seabirds avoid fledging on nights when the moon is fuller [17], yet few studies have assessed this hypothesis [15,18,19].…”

Moonlight diminishes seabird attraction to artificial light

“…To our best knowledge, fledging of cavity‐nesting seabirds is not correlated to the moon cycle. Since the first studies, several authors stated that Newell's shearwaters from cross‐fostered and natural colonies fledged irrespective of the moon phase (Byrd et al, 1984; Telfer et al, 1987), which has been recently corroborated by the use of camera traps (Raine et al, 2023). Preliminary data suggest that Leach's storm‐petrels Hydrobates leucorhous also fledge across the moon cycle (Miles et al, 2010) and a radar survey conducted near a Barau's petrel colony at Réunion Island very convincingly demonstrated that the number of fledglings detected was not influenced by moonlight (Gineste, 2016).…”

“…Evidence from rescue programs supports the hypothesis that increased moonlight reduces the attraction and disorientation of seabirds, consequently reducing fallout magnitude. In species with synchronized breeding cycles, most fledglings leave nests within a period of time that is shorter than one lunar cycle, for example, Cory's shearwater Calonectris borealis (Figure S1; Rodríguez & Rodríguez, 2009), Barau's petrels Pterodroma baraui and wedge‐tailed shearwaters Ardenna pacifica (Chevillon et al, 2022), short‐tailed shearwater Ardenna tenuirostris (Rodríguez et al, 2014), or Newell's shearwater Puffinus newelli (Ainley et al, 2001; Raine et al, 2023). When plotting the number of stranded fledglings per night against the rescue date, we observe clear differences in the rescue patterns and the magnitude of the fallout: full moon is linked to shifts in the peak fallout date by decreasing the number of fledglings grounded during full moon nights (Figure 1).…”

“…Being typically cavity‐nesting species, the limited light coming into nests prevents a growing eye to achieve emmetropia, that is, chicks fledge with an underdeveloped and untrained visual system (Atchoi et al, 2020; Mitkus et al, 2018). However, near‐to‐fledging procellariform chicks emerge from burrows at night to stretch and exercise their wings in the weeks before their departure (Raine et al, 2023; Yoda et al, 2017). So, moonlight during these nights might be enough to provide the needed visual stimuli to develop their visual systems.…”