# Contrasting haemosporidian infections in two ecologically distinct wading birds from breeding colonies in the southeastern United States

## TL;DR

The study compares haemosporidian infections in two wading bird species, finding that white ibis have higher infection rates and may act as parasite reservoirs.

## Contribution

This is the first direct comparison of hemoparasite infections in two ecologically distinct wading bird species using movement data to explain infection differences.

## Key findings

- White ibis had a higher Haemoproteus plataleae infection prevalence (42.1%) compared to tricolored herons (14.5%).
- White ibis used more freshwater habitats, potentially supporting vector habitats, while tricolored herons remained in coastal areas.
- White ibis may serve as major reservoirs for H. plataleae, while tricolored herons may disperse parasites regionally.

## Abstract

Wading birds may serve as ideal hosts for avian hemoparasites, as they are long-lived, undertake extensive movements, form dense breeding colonies, and inhabit water-associated environments that support vectors. Although previous studies have reported parasite species and prevalence in various wading bird species, little is known about their associations with bird behavior and life stage. To address this gap, we examined haemosporidian infections in two ecologically distinct species, white ibis (Eudocimus albus) and tricolored heron (Egretta tricolor), to explore differences in life stage and movement that may explain prevalence differences. We combined blood screening for hemoparasites with satellite tracking data describing birds’ movement patterns. We screened 95 white ibis (67 juveniles and 28 adults or subadults) and 69 tricolored herons (45 juveniles and 24 adults). We detected a single Haemoproteus plataleae lineage in both species, with higher infection prevalence in white ibis (42.1 %) than in tricolored herons (14.5 %). Among white ibis, adults showed a higher prevalence (67.9 %) than juveniles (31.3 %), whereas in tricolored herons, adults had a prevalence of 8.3 % and juveniles 17.8 %. Non-breeding season movement data showed that white ibis used both freshwater and saline habitats across the southeastern United States, which may also serve as habitats for vectors. In contrast, tricolored herons remained mainly along coastal areas, using saline habitats in the southeastern United States and wintering sites in Central America, which may be less favorable for vectors. Overall, white ibis may serve as major reservoirs and sources of reinfection for H. plataleae, whereas tricolored herons may facilitate parasite dispersal between breeding colonies along the coasts of the southeastern United States and wintering areas in Central America. This study presents the first direct comparison of hemoparasite infections in two ecologically distinct wading birds and highlights movement data as key to explaining infection differences, providing a baseline for future studies.

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•Haemoparasite prevalence was higher in white ibis than tricolored herons at breeding colonies in Alabama, USA.•White ibis used higher proportions of freshwater habitats than tricolored herons outside of the breeding season.•Infections occurred across age classes and possibly at both breeding colonies and wintering grounds.•White ibis may act as parasite reservoirs and support reproduction, whereas herons may transmit parasites across regions.

Haemoparasite prevalence was higher in white ibis than tricolored herons at breeding colonies in Alabama, USA.

White ibis used higher proportions of freshwater habitats than tricolored herons outside of the breeding season.

Infections occurred across age classes and possibly at both breeding colonies and wintering grounds.

White ibis may act as parasite reservoirs and support reproduction, whereas herons may transmit parasites across regions.