Within and between species competition in a seabird community: statistical exploration and modeling of time-series data

Abstract

In a changing environment, the maintenance of communities is subject to many constraints (phenology, resources, climate, etc.). One such constraint is the relationship between conspecifics and competitors. In mixed colonies, seabirds may have to cope with interspecific and intraspecific competition for both space and food resources. We applied competitive interaction models to data on three seabird breeding populations: black-legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge) and Brünnich's guillemot (Uria lomvia) collected over 27-years at Kharlov Island in the Barents Sea. We found a competitive effect only for the kittiwake breeding population size on the common guillemot breeding population size when kittiwakes were abundant. The timing of kittiwake breeding negatively affected the number of breeding Brünnich's guillemots. The timing of breeding was negatively correlated to biomass of the main pelagic fish in the Barents Sea, the capelin (Mallotus villosus), which suggests an indirect action. The community matrix shows that the community was not stable. The kittiwake population did not decrease as seen in north Norwegian populations. Likewise, the common guillemot population, after a crash in 1985, was recovering at Kharlov while Norwegian populations were decreasing. Only the Brünnich's guillemot showed a decrease at Kharlov until 1999. We suggest that the stability of the kittiwake and common guillemot populations at Kharlov is due to better feeding conditions than in colonies of the Norwegian coast, linked to a possible eastward shift of the capelin population with the temperature increase of the Barents Sea.

Testing for effects of climate change on competitive relationships and coexistence between two bird species

“…At the species level, competition may lead to exclusion if one species experiences a greater competitive effect from another species than within its own species [2,3]. Theoretical [3] and empirical [4,5] investigations have indicated the importance of both competition and the environment in predicting species composition, diversity and niche overlap in ecological communities. However, conclusive demonstrations of competitive exclusion are rare.…”

Temporal Dynamics of Top Predators Interactions in the Barents Sea

“…Since it was shown that the kittiwake is a competitor to the common guillemot [20], the mirror response may reflect that what is good for kittiwake is bad for the guillemot hence the remarkably similar inflection point in sea temperature at ca 4°C for both species. The change in their diet is explained by climatic variables such as sea temperature, that may be a proxy of the local condition in term of prey availability spectrum.…”

“…Overlap in diet between species j and k is complete when O jk  = 1 and is absent when O jk  = 0 [20], [41]. Values exceeding 0.6 are considered to represent “biologically significant” overlap in diet composition [42].…”

“…Values exceeding 0.6 are considered to represent “biologically significant” overlap in diet composition [42]. However, we considered that when mean O jk >2˙SD the diet overlap between species j and species k is significant [20], [41].…”

“…The top-predator (species at the top of their food chain) community in the Barents Sea consists of about 33 seabird species [19] and 21 mammal species [16], in addition to large demersal fish, of which cod is the most abundant species. Interactions between several of these species have previously been identified, such as between the Black-legged kittiwake Rissa tridactyla and the Common guillemot Uria aalge [20], between the Minke whale Balaenoptera acutorostrata and the NEA cod [21], and between the harp seal and the NEA cod [22]. Such interactions should be included when investigating population dynamics in an ecosystem context, i.e., taking into account species interactions.…”