Trends in reproductive success of Hawaiian seabirds: is guild membership a good criterion for choosing indicator species?

Abstract

Because it is rarely possible to monitor all species that occur in sensitive or threatened ecosystems, much theoretical consideration has been given to the process of choosing indicator species. We evaluated whether foraging guild classification or nest site might be an adequate means to select indicator species for monitoring the reproductive success of a suite of Hawaiian seabird species. We examined the reproductive success of six species representing three foraging guilds and two types of nest sites over an 18-year period. For two of the three foraging guilds, there was a strong correlation between the reproductive success of birds from the same guild, and there was a weaker correlation for the third guild. In contrast, there were no significant reproductive success correlations for pairs of species from different foraging guilds but with the same nest sites. Thus, the within-guild correlations are likely to be driven by guild-specific food availability rather than by similarity in nest site. Because of the weak nature of one of the within-guild correlations, and because there is little detailed information on the causes of nest failure in this system, we recommend continuing to monitor multiple indicator species per foraging guild.