Parasite assemblages of Double-crested Cormorants as indicators of host populations and migration behavior

Abstract

The Double-crested Cormorant (Phalacrocorax auritus) is culled in many states because of the real and presumed damages it inflicts on farmed and recreational fisheries and other ecosystem services. Resident cormorant colonies breeding in the southeastern United States are protected in some areas, so it is important to distinguish these from co-occurring but unprotected migratory cormorants. Migratory P. auritus are likely to contain helminthic parasite communities that differ from those of non-migratory, resident birds, because they will encounter a wider variety of habitats and intermediate host communities during migrations. Here, we document five distinct assemblages of helminth parasites collected from 218 P. auritus culled from 11 sites in Alabama, Minnesota, Mississippi, and Vermont. The assemblages of P. auritus parasites are distinct among many sampling locations and can be used to correctly predict where a host cormorant has been feeding. We provide evidence for mixing of cormorants at a regional scale using discriminant analysis, which suggests there is a single population of migratory cormorants. Furthermore, our models strongly differentiate between migratory

Animal migrations and parasitism: reciprocal effects within a unified framework

“…Parasitic species carried by migrants have long been used as markers to identify their area of origin or reconstruct the route followed during migration in fish (e.g. Criscione, Cooper & Blouin, 2006; Alarcos & Timi, 2013; Jacobson et al ., 2019), birds (Durrant et al ., 2008; Sheehan et al ., 2016) and mammals (Iwasa‐Arai et al ., 2018). However, parasites are not just passive passengers that convey useful information: they are increasingly considered as potential drivers of animal migrations, since the diseases they cause represent another environmental pressure, like food scarcity or high predation risk, that animals may avoid by moving to a different habitat (Piersma, 1997; Altizer, Bartel & Han, 2011; Møller & Szép, 2011; Shaw & Binning, 2016).…”

Helminths of the mallardAnas platyrhynchosLinnaeus, 1758 from Austria, with emphasis on the morphological variability ofPolymorphus minutusGoeze, 1782

“…Such analyses have been described as useful tools in many aspects of ecology, including parasite infracommunity ecology (Simberloff & Moore, 1997). Even on a small scale such analyses can be helpful, as shown, for example, by Sheehan et al (2016) who distinguished between migrating and stationary cormorant populations by analysing their helminth communities. The presence or the absence of a parasite in an ecosystem may indicate the presence or absence of its definitive host, even if it has not been observed.…”

Conspecific migration and environmental setting determine parasite infracommunities of non-migratory individual fish

“…Parasites have often been used to trace the migratory behaviour of their hosts and discriminate host stocks in the sea, but rarely in freshwater (e.g. Carballo et al ., 2012 ; Sheehan et al ., 2016 ; Irigoitia et al ., 2017 ; Canel et al ., 2019 ). However, migration is a heterogeneous phenomenon, varying both between and within species.…”