Egg shape and color mediate acceptance thresholds in diverse avian host species with different rates of antiparasitic egg rejection.

Eggshell recognition in parental birds is vital for nest management, defense against brood parasitism, optimal embryonic development, and minimizing disease and predation risks. This process relies on acceptance thresholds balancing the risk of rejecting own eggs against the benefit of excluding foreign ones, following signal detection theory. We investigated the role of object shape in egg rejection decisions among three host species of the brown-headed cowbird (Molothrus ater), each with a varying known response to parasitic eggs.

The Implications of Atlantic Salmon ( L.) Fatty Acid Profiles for Their Thiamine Status.

Thiamine deficiency is an ongoing issue across the Northern Hemisphere, causing reproductive failure in multiple salmonid populations. In the Baltic Sea, a large brackish water system in northern Europe, previous research has suggested that this deficiency is associated with lipid-rich diets with a high proportion of docosahexaenoic acid (DHA, 22:6n-3). The mechanism proposed is that a diet abundant in highly unsaturated fatty acids, such as DHA, depletes thiamine as an antioxidant defense in adult salmonids, rather than allocating thiamine to the offspring.

Highly virulent avian brood-parasitic species show elevated embryonic metabolic rates at specific incubation stages compared to less virulent and non-parasitic species.

As the avian embryo grows and develops within the egg, its metabolic rate gradually increases. Obligate avian brood-parasitic birds lay their eggs in the nests of other species to avoid the costs of parental care, and all but one of these brood-parasitic species are altricial at hatching. Yet the chicks of some altricial brood-parasitic species perform the physically demanding task of evicting, stabbing or otherwise killing host progeny within days of hatching.

Enhancing nitrogen removal through macrophyte harvest and installation of woodchips-based floating beds in surface-flow constructed wetlands.

Wetland management maintains nitrogen (N) removal capacity in mature and overgrown constructed wetlands (CWs). We evaluated whether CW management by macrophyte harvesting, and subsequent installation of woodchips-based floating beds (WFBs) planted with Glyceria maxima and Filipendula ulmaria improved N removal. In sixteen heavily overgrown experimental CWs, we applied four treatments: i) only macrophyte harvesting, ii) 5% of the harvested-CW surface covered with WFBs, iii) 20% WFBs cover, and iv) a control treatment (heavily overgrown).

Colonial breeding impacts potentially fitness-relevant cognitive processes in barn swallows.

Many animals breed colonially, often in dense clusters, representing a complex social environment with cognitive demands that could ultimately impact individual fitness. However, the effects of social breeding on the evolution of cognitive processes remain largely unknown. We tested the hypothesis that facultative colonial breeding influences attention and decision-making.

Plumage and eggshell colouration covary with the level of sex-specific parental contributions to nest building in birds.

Interspecific variation in sex-specific contributions to prenatal parental care, including avian nest building, is becoming increasingly better understood as we amass more information on more species. We examined whether sex-specific nest building contributions covary with the colouration of parents and their eggs in 521 species of Western Palearctic birds. Having colourful plumage and laying colourful eggs are costly because of the deposition of pigments in feathers and eggs and/or forming costly nanostructural substrates in feathers, and so it might be expected that those costs covary with the costs of nest building at the level of individuals and/or across species to produce of a suite of codivergent traits.

Host avian species and environmental conditions influence the microbial ecology of brood parasitic brown-headed cowbird nestlings: What rules the roost?

The role of species interactions, as well as genetic and environmental factors, all likely contribute to the composition and structure of the gut microbiome; however, disentangling these independent factors under field conditions represents a challenge for a functional understanding of gut microbial ecology. Avian brood parasites provide unique opportunities to investigate these questions, as brood parasitism results in parasite and host nestlings being raised in the same nest, by the same parents. Here we utilized obligate brood parasite brown-headed cowbird nestlings (BHCO; Molothrus ater) raised by several different host passerine species to better understand, via 16S rRNA sequencing, the microbial ecology of brood parasitism.

Nestling Begging Calls Resemble Maternal Vocal Signatures When Mothers Call Slowly to Embryos.

AbstractVocal production learning (the capacity to learn to produce vocalizations) is a multidimensional trait that involves different learning mechanisms during different temporal and socioecological contexts. Key outstanding questions are whether vocal production learning begins during the embryonic stage and whether mothers play an active role in this through pupil-directed vocalization behaviors. We examined variation in vocal copy similarity (an indicator of learning) in eight species from the songbird family Maluridae, using comparative and experimental approaches.

Nest architecture influences host use by avian brood parasites and is shaped by coevolutionary dynamics.

Brood (social) parasites and their hosts exhibit a wide range of adaptations and counter-adaptations as part of their ongoing coevolutionary arms races. Obligate avian brood parasites are expected to use potential host species with more easily accessible nests, while potential hosts are expected to evade parasitism by building more concealed nests that are difficult for parasites to enter and in which to lay eggs. We used phylogenetically informed comparative analyses, a global database of the world's brood parasites, their host species, and the design of avian host and non-host nests (approx.

Host learning selects for the coevolution of greater egg mimicry and narrower antiparasitic egg-rejection thresholds.

Egg rejection is an effective and widespread antiparasitic defense to eliminate foreign eggs from the nests of hosts of brood parasitic birds. Several lines of observational and critical experimental evidence support a role for learning by hosts in the recognition of parasitic versus own eggs; specifically, individual hosts that have had prior or current experience with brood parasitism are more likely to reject foreign eggs. Here we confirm experimentally the role of prior experience in altering subsequent egg-rejection decisions in the American robin , a free-living host species of an obligate brood parasite, the brown-headed cowbird .

Sensory collectives in natural systems.

Groups of animals inhabit vastly different sensory worlds, or umwelten, which shape fundamental aspects of their behaviour. Yet the sensory ecology of species is rarely incorporated into the emerging field of collective behaviour, which studies the movements, population-level behaviours, and emergent properties of animal groups. Here, we review the contributions of sensory ecology and collective behaviour to understanding how animals move and interact within the context of their social and physical environments.

Biogeographic history, egg colouration, and habitat selection in Turdus thrushes (Aves: Turdidae).

Despite broad interest and recent experimentation, there is no single ecological model accounting for the adaptive significance of the diversity of avian eggshell colouration. The often blue-green eggs of Turdus thrushes are a charismatic example of this, having long captured cultural and scientific attention. Although the biology and evolutionary history of "true" thrushes is well understood, little is known about correlated evolution between shifts in habitat and eggshell pigmentation, and how these shifts map with Turdus biogeography.

Following the feeder: A global synthesis of disturbance-based foraging associations of birds.

Species interactions link animal behaviour to community structure and macroecological patterns of biodiversity. One common type of trophic species interaction is disturbance foraging-the act of obtaining food at a disturbance created by another organism. Disturbance foraging is widespread across the animal kingdom, especially among birds, yet previous research has been largely anecdotal and we still lack a synthetic understanding of how this behaviour varies geographically, phylogenetically and ecologically.

Thiamin dynamics during the adult life cycle of Atlantic salmon (Salmo salar).

Thiamin is an essential water-soluble B vitamin known for its wide range of metabolic functions and antioxidant properties. Over the past decades, reproductive failures induced by thiamin deficiency have been observed in several salmonid species worldwide, but it is unclear why this micronutrient deficiency arises. Few studies have compared thiamin concentrations in systems of salmonid populations with or without documented thiamin deficiency.

What's the rumpus? Resident temperate forest birds approach an unfamiliar neotropical alarm call across three continents.

Alarm signals have evolved to communicate pertinent threats to conspecifics, but heterospecifics may also use alarm calls to obtain social information. In birds, mixed-species flocks are often structured around focal sentinel species, which produce reliable alarm calls that inform eavesdropping heterospecifics about predation risk. Prior research has shown that Neotropical species innately recognize the alarm calls of a Nearctic sentinel species, but it remains unclear how generalizable or consistent such innate signal recognition of alarm-calling species is.

The evolutionary ecology of nests: a cross-taxon approach.

Nests, including the enormous structures housing colonies of eusocial insects and the elaborately built nests of some fishes, have long fascinated scientists, yet our understanding of the evolutionary ecology of nests has lagged behind our understanding of subsequent reproductive stages. There has, however, been a burgeoning amount of interest in nests over the past decade, and this special issue on 'The evolutionary ecology of nests: a cross-taxon approach' outlines our understanding of the form and function of nests in diverse animal lineages. Papers in 'The function of nests: mechanisms and adaptive benefits' theme examine the various functions of nests, while papers in 'The evolution of nest characteristics' theme examine the evolution of nesting behaviours.

The evolution of nest site use and nest architecture in modern birds and their ancestors.

The evolution of nest site use and nest architecture in the non-avian ancestors of birds remains poorly understood because nest structures do not preserve well as fossils. Nevertheless, the evidence suggests that the earliest dinosaurs probably buried eggs below ground and covered them with soil so that heat from the substrate fuelled embryo development, while some later dinosaurs laid partially exposed clutches where adults incubated them and protected them from predators and parasites. The nests of euornithine birds-the precursors to modern birds-were probably partially open and the neornithine birds-or modern birds-were probably the first to build fully exposed nests.

Decision rules for egg-color-based rejection by two cavity-nesting hosts of the brown-headed cowbird.

Hosts of obligate avian brood parasites often evolve defense mechanisms to avoid rearing unrelated young. One common defense is egg rejection, for which hosts often rely on eggshell color. Most research has assumed that hosts respond to perceived color differences between their own eggs and parasite eggs regardless of the particular color; however, recent experiments have found that many hosts respond more strongly to brown foreign eggs than to equally dissimilar blue eggs.

Female red-winged blackbirds (Agelaius phoeniceus) do not alter nest site selection, maternal programming, or hormone-mediated maternal effects in response to perceived nest predation or brood parasitism risk.

Predation or brood parasitism risks can change the behaviors and reproductive decisions in many parental animals. For oviparous species, mothers can mitigate their reproductive success in at least three ways: (1) by avoiding nest sites with high predation or parasitism risks, (2) through hormonal maternal effects that developmentally prime offspring for survival in risky environments, or (3) by investing less in reproduction when predation or parasitism risks are high. Here, we tested if perceived predation and parasitism risks can induce any of these behavioral or physiological responses by exposing female red-winged blackbirds (Agelaius phoeniceus) to playbacks of two major nest threats, a predator (Cooper's hawk, Accipiter cooperii) and an obligate brood parasite (brown-headed cowbird; Molothrus ater), as well as two controls (harmless Eastern meadowlark, Sturnella magna; and silence).

Gradual changes in model shape affect egg-directed behaviours by parasitic shiny cowbirds in captivity.

Eggs are critically important for avian reproduction as all birds are oviparous. Accordingly, the recognition and care of own eggs represent the cornerstones of avian breeding, whereas the elimination of foreign objects, including brood-parasitic eggs and non-egg items from the nest are known to also increase fitness by refocusing incubation effort on the parents' own eggs. But egg recognition also plays a role in some avian obligate brood parasites' reproductive strategy through the pecking of already present eggs in the hosts' clutch to reduce nestmate competition with the parasite's own hatchling.

Machine learning and statistical classification of birdsong link vocal acoustic features with phylogeny.

Birdsong is a longstanding model system for studying evolution and biodiversity. Here, we collected and analyzed high quality song recordings from seven species in the family Estrildidae. We measured the acoustic features of syllables and then used dimensionality reduction and machine learning classifiers to identify features that accurately assigned syllables to species.