Modeling territory attendance and preening behavior in a seabird colony as functions of environmental conditions

Extrinsic stressors modulate resource evaluations: insights from territoriality under artificial noise

Background

Competition is considered to rely on the value attributed to resources by animals, but the influence of extrinsic stressors on this value remains unexplored. Although natural or anthropogenic environmental stress often drives decreased competition, assumptions that this relies on resource devaluation are without formal evidence. According to theory, physiological or perceptual effects may influence contest behaviour directly, but motivational changes due to resource value are expected to manifest as behavioural adjustments only in interaction with attainment costs and resource benefits. Thus, we hypothesise that stressor-induced resource devaluations will impose greater effects when attainment costs are high, but not when resource benefits are higher. Noise may elicit such effects because it impacts the acoustic environment and imposes physiological and behavioural costs to animals. Therefore, we manipulated the acoustic environment using playbacks of artificial noise to test our hypotheses in the territorial male Siamese fighting fish, Betta splendens.

Results

Compared to a no-playback control, noise reduced defense motivation only when territory owners faced comparatively bigger opponents that impose greater injury costs, but not when territories also contained bubble nests that offer reproductive benefits. In turn, nest-size decreases were noted only after contests under noise treatment, but temporal nest-size changes relied on cross-contest variation in noise and comparative opponent size. Thus, the combined effects of noise are conditional on added attainment costs and offset by exceeding resource benefits.

Conclusion

Our findings provide support for the hypothesised modulation of resource value under extrinsic stress and suggest implications for competition under increasing anthropogenic activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12983-021-00397-x.

Feather mite abundance varies but symbiotic nature of mite-host relationship does not differ between two ecologically dissimilar warblers

Feather mites are obligatory ectosymbionts of birds that primarily feed on the oily secretions from the uropygial gland. Feather mite abundance varies within and among host species and has various effects on host condition and fitness, but there is little consensus on factors that drive variation of this symbiotic system. We tested hypotheses regarding how within-species and among-species traits explain variation in both (1) mite abundance and (2) relationships between mite abundance and host body condition and components of host fitness (reproductive performance and apparent annual survival). We focused on two closely related (Parulidae), but ecologically distinct, species: Setophaga cerulea (Cerulean Warbler), a canopy dwelling open-cup nester, and Protonotaria citrea (Prothonotary Warbler), an understory dwelling, cavity nester. We predicted that feather mites would be more abundant on and have a more parasitic relationship with P. citrea, and within P. citrea, females and older individuals would harbor greater mite abundances. We captured, took body measurements, quantified feather mite abundance on individuals' primaries and rectrices, and monitored individuals and their nests to estimate fitness. Feather mite abundance differed by species, but in the opposite direction of our prediction. There was no relationship between mite abundance and any measure of body condition or fitness for either species or sex (also contrary to our predictions). Our results suggest that species biology and ecological context may influence mite abundance on hosts. However, this pattern does not extend to differential effects of mites on measures of host body condition or fitness.

Seasonal and daily changes in the behaviour of the adult emu (Dromaius novaehollandiae) under farm conditions

1. The aim of this study was to present selected elements of emu behaviour in three different seasons (the non-breeding season, the pre-breeding season and the breeding season) and in the morning and afternoon. The study focused on feed, water and sand intake; plumage care; resting; agonistic behaviour and other activities, mostly standing still, aimless walking or observing the surroundings. 2. The troop consisted of 11 emus (5 females and 6 males) aged 12 years, kept in a free-range system. Observations were carried out during a period of 3 weeks in each season, during which 60-min observation sessions took place on 3 randomly chosen days. 3. A significant effect was found of each season on the behaviour patterns related to feeding, sand intake, plumage care, resting and agonistic behaviour. 4. Time of day affected the behaviour associated with the collection of food and water, foraging, pecking and ingesting sand and plumage preening. 5. Most of the time, regardless of season and time of day, the emus were standing still, walking aimlessly or observing the surrounding area.

Coping behaviour as an adaptation to stress: post-disturbance preening in colonial seabirds

In humans, coping behaviour is an action taken to soothe oneself during or after a stressful or threatening situation. Some human behaviours with physiological functions also serve as coping behaviours, for example, comfort sucking in infants and comfort eating in adults. In birds, the behaviour of preening, which has important physiological functions, has been postulated to soothe individuals after stressful situations. We combine two existing modelling approaches - logistic regression and Darwinian dynamics - to explore theoretically how a behaviour with crucial physiological function might evolve into a coping behaviour. We apply the method to preening in colonial seabirds to investigate whether and how preening might be co-opted as a coping behaviour in the presence of predators. We conduct an in-depth study of the environmental correlates of preening in a large gull colony in Washington, USA, and we perform an independent field test for comfort preening by computing the change in frequency of preening in gulls that were alerted to a predator, but did not flee.

Can preening contribute to influenza A virus infection in wild waterbirds?

Wild aquatic birds in the Orders Anseriformes and Charadriiformes are the main reservoir hosts perpetuating the genetic pool of all influenza A viruses, including pandemic viruses. High viral loads in feces of infected birds permit a fecal-oral route of transmission. Numerous studies have reported the isolation of avian influenza viruses (AIVs) from surface water at aquatic bird habitats. These isolations indicate aquatic environments have an important role in the transmission of AIV among wild aquatic birds. However, the progressive dilution of infectious feces in water could decrease the likelihood of virus/host interactions. To evaluate whether alternate mechanisms facilitate AIV transmission in aquatic bird populations, we investigated whether the preen oil gland secretions by which all aquatic birds make their feathers waterproof could support a natural mechanism that concentrates AIVs from water onto birds' bodies, thus, representing a possible source of infection by preening activity. We consistently detected both viral RNA and infectious AIVs on swabs of preened feathers of 345 wild mallards by using reverse transcription–polymerase chain reaction (RT-PCR) and virus-isolation (VI) assays. Additionally, in two laboratory experiments using a quantitative real-time (qR) RT-PCR assay, we demonstrated that feather samples (n = 5) and cotton swabs (n = 24) experimentally impregnated with preen oil, when soaked in AIV-contaminated waters, attracted and concentrated AIVs on their surfaces. The data presented herein provide information that expands our understanding of AIV ecology in the wild bird reservoir system.