Ecological niche partitioning in two Pacific puffins

Abstract

Ecological theory predicts that closely related species can coexist if they segregate in space, time, or diet to reduce competitive overlap when resources are limited. These differences in ecological niche are presumably driven by concomitant differences in morphology. The link between form and functional segregation may only occur at 1 period of the year, and while examining behavioural differences among closely related species across the whole annual cycle can answer this question, it is rarely tested. Here, we investigated niche partitioning between sister species within the puffin clade: tufted puffins Fratercula cirrhata with high wing loading and rhinoceros auklets Cerorhinca monocerata with low wing loading, breeding in sympatry on Middleton Island, Alaska. We collected data for horizontal movement, dive depth, and trophic ecology. Tufted puffins dived deeper, foraged closer to the colony during breeding, and migrated shorter distances relative to rhinoceros auklets. Examination of allometric patterns further revealed that puffins exceeded the predicted dive duration limit with exceptionally long dives. However, isotopic niches of the 2 species were very similar. Rhinoceros auklet breeding phenology was about 3 wk earlier than tufted puffin phenology, and breeding success during the study period was always higher for auklets than puffins. We conclude that the 2 species of sympatric puffin partitioned both in space and time throughout the annual cycle, illustrating how such partitioning can facilitate the coexistence of seabirds sharing apparently similar space.

Variations in inter‐specific and sex‐related niche partitioning in pelagic boobies during their annual cycle

“…Examples of intra‐specific niche partitioning are particularly common in species with sexual size dimorphism (Lerma, Dehnhard, et al., 2020 ; Mancini et al., 2013 ; Phillips et al., 2017 ). Inter‐ and intra‐specific differences are often linked to differences in body size, with larger individuals or species dominating in areas with higher prey availability (Catry et al., 2005 ; Phillips et al., 2017 ; Selander, 1966 ), using different foraging areas (Shoji et al., 2023 ; Weimerskirch et al., 2009 ; Zavalaga et al., 2007 , 2010 ), or feeding on a greater range of prey sizes (Cohen et al., 1993 ; Mancini & Bugoni, 2014 ). In contrast, smaller individuals or species might be more agile, travel longer distances, or specialize in smaller prey, thanks to their lower energetic constraints (Ballance et al., 1997 ; Mancini et al., 2014 ; Shoji et al., 2023 ; Weimerskirch et al., 2006 ).…”

“…Nitrogen isotopes (δ 15 N) increase predictably from prey to predator and are a useful proxy for the trophic position of the organism (DeNiro & Epstein, 1981 ; Hobson & Clark, 1992 ), while carbon isotopes (δ 13 C) increase predictably from inshore to offshore food webs (Cherel & Hobson, 2007 ). The isotopic niche and its dimensions have thus been used to study the trophic ecology and niches of several marine predators including fish (Kojadinovic et al., 2008 ; Teffer et al., 2015 ), sharks (Lear et al., 2021 ), cetaceans (Peters et al., 2022 ), and many species of seabirds (Kojadinovic et al., 2008 ; Navarro et al., 2015 ; Robertson et al., 2014 ; Shoji et al., 2023 ).…”