Foraging interactions between wading birds and strand-feeding bottlenose dolphins (Tursiops truncatus) in a coastal salt marsh

Abstract

Strand-feeding is a unique foraging technique used by Atlantic bottlenose dolphins ( Tursiops truncatus (Montagu, 1821)) in salt marshes of the southeastern USA wherein a group of dolphins rushes a creek bank, temporarily stranding themselves to capture fish that have been pushed ashore by their bow wave. Wading birds are attracted to these events to forage on stranded fish. We hypothesized that birds foraging in association with dolphins experience greater foraging efficiency than birds foraging away from dolphins and that some birds are able to meet their entire daily metabolic needs by foraging at strand-feeding events. The species composition, abundance, and foraging success of birds at 569 strand-feeding events were compared with the same parameters from marsh surveys of birds not associated with dolphins. Only Great Egrets ( Ardea alba L., 1758) were proportionately more common at strand-feeding events than in the marsh overall (p < 0.001). During peak strand-feeding hours, energy intake per hour was higher for Great Egrets foraging with strand-feeding dolphins than for birds foraging away from dolphins (p = 0.04). Bioenergetic models indicated that prey intake by Great Egrets at strand-feeding events was sufficient to meet their existence and likely their active metabolic requirements.

Seabird and dolphin associations: do seabirds benefit from feeding in association with dusky dolphins in Patagonia?

“…Hence, the association appears to be one of facultative commensalism. This type of feeding relationship was also described by Bräger (1998) in his observations of seabirds associating with Hector's dolphins, and by Fox & Young (2012), who found a commensal relationship between two apex predators, one terrestrial (wading birds) and one marine (strand-feeding dolphins). In this case, the foraging activities of the dolphins regularly allow individual birds to meet their energy requirements by providing access to normally inaccessible prey.…”

A remote marking device and newly developed permanent dyes for Wildlife research

“…Donehower and Bird () state likewise that the technique of self‐marking by birds where dye is placed in the nest is not good because the pattern of dye is more random and individuals cannot be marked at a targeted part of their bodies. The same is true for techniques such as paintball land mines Fox () and eggshells or light bulbs thrown at birds (Bendell and Fowle ).…”

“…However, ingredients in Drimark dyes might be unsafe because they contain toxic ingredients (commercial dye in a highly volatile organic carrier solvent, methyl isobutyl ketone–n‐butyl acetate, diethylene glycol monobutyl ether–ethyl acetate–poly ethylene glycol, or polycarboxylic acid, and has metallic dye particles suspended in a resin polymer, Sukhna and Reichmann ). Vegetable and commercial wool dyes, and stamp‐pad ink did not last for >2 weeks (Kennard []); and ink‐jet printer ink ran when in contact with water (Fox ). The ink is also basic and thus similar to textile dyes (Nyman and Hakala ).…”

Dorsal fin mark changes for assigning sexes to individual bottlenose dolphins, Tursiops truncatus

“…Knowing the sex of individuals in populations under threat or with high exposure to human impacts can be valuable for conservation efforts, due to intersexual and interindividual differences in temporal and spatial habitat use as well as behaviors (social and foraging). Use of risky foraging strategies, e.g., strand feeding (Fox & Young, 2012;Jiménez & Alava, 2015) and provisioning (Foroughirad & Mann, 2013)…”