Animal culture research should include avian nest construction

Material culture—that is, group-shared and socially learned object-related behaviour(s)—is a widespread and diverse phenomenon in humans. For decades, researchers have sought to confirm the existence of material culture in non-human animals; however, the main study systems of interest—namely, tool making and/or using non-human primates and corvids—cannot provide such confirmatory evidence: because long-standing ethical and logistical constraints handicap the collection of necessary experimental data. Synthesizing evidence across decades and disciplines, here, I present a novel framework for (mechanistic, developmental, behavioural, and comparative) study on animal material culture: avian nest construction.

Does the intrusion of an avian nest predator elicit a change in the behaviour of a canopy-nesting passerine?

Many studies have shown that nest predators affect their prey indirectly by inducing changes in the behaviour of the prey. Studies suggest that the type and degree of nest defence strategies depends heavily on species, along with nest type and location. One such strategy, nest vigilance, allows individuals to collect information and make informed decisions based on their surroundings. In this study, we simulated the intrusion of a common avian nest predator (blue jay, Cyanocitta cristata) into the territory of nesting cerulean warblers (Setophaga cerulea) and evaluated eight different behavioural variables to determine their response to the nest predator. Female cerulean warblers were more vigilant on their nest when exposed to a potential predator compared to a nest with lower threat of predation. Females exposed to a nest predator increased incubation bout by 109% and brooding bout by 60%. Our data also suggest that male cerulean warblers reduce their provisioning rate during the early nestling stage (−1 feeding/hour) and late nestling stage (−3 feedings/hour), although more data are needed. Modification of incubation bout length and nestling provisioning rate are common strategies employed by songbirds to reduce activity around the nest, by decreasing detection opportunities of visually-oriented nest predators. Currently, the only understanding we have on how cerulean warblers respond to a nest predator is based on observational data. The results of this study provide the first evidence that cerulean warblers are able to identify species that pose a threat to the safety of their nest, and that they modify their behaviour to reduce nest detection by predators. The results of this study provide a better understanding of a relatively unknown aspect of the breeding behaviour of this species. This study is also first to describe how an open-cup, canopy-nesting species responds to an increase in nest predation threat.

Arboreal aperitifs: Space use and activity of a major songbird nest predator in a tropical Thailand forest

ABSTRACTPredator-prey interactions are fundamental drivers of population dynamics, yet rarely are both predator and prey species simultaneously studied. Despite being significant, widespread avian nest predators, research on the ecology of Southeast Asian snakes in relation to birds remains scarce. The green cat snake (Boiga cyanea) is a primary nest predator, responsible for ≈24% of forest songbird depredation in Northeast Thailand. We explored both diurnal and nocturnal movements of 14 (5 male, 9 female) adult B. cyanea with radio-telemetry for an average of 68 ± 16 days per individual, between 21 October 2017 and 8 June 2019 in the dry evergreen forest of the Sakaerat Biosphere Reserve (SBR). We quantified area of space use (ha) and activity through motion variance (Ϭm2) during the study period using dynamic Brownian bridge movement models, and linked our findings to a simultaneously-run avian nest monitoring study, initiated in 2013 within the same forest fragment. On average, movements, space use and activity differed between males and females, and between the avian nesting and non-nesting seasons. Males moved 51.37 m/day farther than females. They used areas 15.09 ha larger than females, and their activity was 3.91 Ϭm2 higher than that of females. In general, individuals moved 50.30 m/day farther during the nesting season than the non-nesting season. The snakes used areas 9.84 ha larger during the nesting season than the non-nesting season, and their activity during the nesting season was 3.24 Ϭm2 higher than that during the non-nesting season. All individuals were exclusively nocturnal, moving throughout the night, and often descending from higher diurnal refugia (>2 m) to forage closer to the ground after sunset. Boiga cyanea activity followed a similar trend to that of the recorded nest depredations at SBR. Our study links snake activity to nest depredations in SBR. Our openly-available data may yield further insight when combined with other major avian nest predator species like the congeneric invasive brown tree snake (Boiga irregularis) on the island of Guam.

Nest ornaments and feather composition form an extended phenotype syndrome in a wild bird

Many species throughout the animal kingdom construct nests for reproduction. A nest is an extended phenotype—a non-bodily attribute—of the individual building it. In some bird species, including our study population of blue tits (Cyanistes caeruleus), conspicuous feathers or other material are placed on top of the nest. These so-called nest ornaments do not contribute to nest insulation, but are hypothesised to have a signalling function. Here, we apply the concept of behavioural syndromes, with focus on between-individual variation (repeatability) and between-individual correlations, to the study of avian nest construction. We find that nest ornamentation is a moderately repeatable trait in female blue tits, which suggests it is an extended phenotype of the female. Furthermore, the tendency to ornament the nest covaries across females with another aspect of her extended phenotype, the composition of the nest lining material, and these two traits thus form an extended phenotype syndrome. Assuming the correlation is reflected on a genetic level, it implies that nest ornamentation and composition of the nest lining do not evolve in isolation; one aspect may be an evolutionary by-product of selection on the other aspect and their overall flexibility to respond to change is reduced. Significance statement The avian nest is an extended phenotype (a non-bodily attribute) of its builder with potentially multiple functions in terms of insulation and signalling. In particular, many bird species’ nests contain nest ornaments, feathers or other materials that are placed on top of the nest and that stand out from the nest material due to their colour and/or size. We quantified between-individual variation (repeatability) of nest ornamentation behaviour in a wild population of blue tits and between-individual covariation (syndrome) of nest ornamentation to other features of nest construction. We find that nest ornamentation is a repeatable trait limited to females in our study population. The tendency to ornament the nest covaries across females with another aspect of her extended nest phenotype, the composition of the nest lining material. These correlated traits thus form an extended phenotype syndrome. It hence becomes crucial to recognise that a study of a single aspect of nest construction in isolation captures only a part of the complexity, as one aspect may have evolved as a correlated response of selection on the other aspect. Moreover, such a syndrome implies limited flexibility in the range of adaptive response.

Hopping species and borders: detection of Bartonella spp. in avian nest fleas and arctic foxes from Nunavut, Canada

Background In a warmer and more globally connected Arctic, vector-borne pathogens of zoonotic importance may be increasing in prevalence in native wildlife. Recently, Bartonella henselae, the causative agent of cat scratch fever, was detected in blood collected from arctic foxes (Vulpes lagopus) that were captured and released in the large goose colony at Karrak Lake, Nunavut, Canada. This bacterium is generally associated with cats and cat fleas, which are absent from Arctic ecosystems. Arctic foxes in this region feed extensively on migratory geese, their eggs, and their goslings. Thus, we hypothesized that a nest flea, Ceratophyllus vagabundus vagabundus (Boheman, 1865), may serve as a vector for transmission of Bartonella spp. Methods We determined the prevalence of Bartonella spp. in (i) nest fleas collected from 5 arctic fox dens and (ii) 37 surrounding goose nests, (iii) fleas collected from 20 geese harvested during arrival at the nesting grounds and (iv) blood clots from 57 adult live-captured arctic foxes. A subsample of fleas were identified morphologically as C. v. vagabundus. Remaining fleas were pooled for each nest, den, or host. DNA was extracted from flea pools and blood clots and analyzed with conventional and real-time polymerase chain reactions targeting the 16S-23S rRNA intergenic transcribed spacer region. Results Bartonella henselae was identified in 43% of pooled flea samples from nests and 40% of pooled flea samples from fox dens. Bartonella vinsonii berkhoffii was identified in 30% of pooled flea samples collected from 20 geese. Both B. vinsonii berkhoffii (n = 2) and B. rochalimae (n = 1) were identified in the blood of foxes. Conclusions We confirm that B. henselae, B. vinsonii berkhoffii and B. rochalimae circulate in the Karrak Lake ecosystem and that nest fleas contain B. vinsonii and B. henselae DNA, suggesting that this flea may serve as a potential vector for transmission among Arctic wildlife.

It’s not all about temperature: breeding success also affects nest design

There are numerous observational studies on intraspecific variation in avian nest building and a single experimental manipulation. The general consensus is that birds build nests in response to environmental conditions, but it is not clear whether such flexibility in nest building is reproductively advantageous. To test the relationship between building flexibility and reproductive success, we allowed captive zebra finches to build their first nest, using string, and to breed in temperature-controlled rooms held at 14 or 30 °C. Once the offspring had fledged, we returned half the pairs to breed at the same temperature while half the pairs were switched to the alternative temperature. We provided all pairs with string and left them to build and breed a second time. For their first nest, pairs that built at 14 °C used more string than did pairs that built at 30 °C, and pairs that bred successfully built a nest with more string than did unsuccessful pairs. When pairs built their second nest, however, temperature no longer explained the number of pieces of string they used; rather, irrespective of the ambient temperature, pairs that had successfully produced young from their first nest used the same amount of string for their second nest, whereas those that had failed to reproduce with their first nest used more string. These latter pairs were then more likely to reproduce successfully. Ambient temperature, therefore, did affect the nest the pairs built but only in the absence of reproductive experience.

Nest Association between Camponotus fallax (Hymenoptera: Formicidae) and Vespa crabro (Hymenoptera: Vespidae) in Central Iberian Peninsula

Because social wasps often defend their nests by inflicting painful stings or bites, some animals associate with them looking for protection against potential predators. Some neotropical vespids are known to maintain associations with other insect and vertebrate taxa, such as birds and bats, however there are not previous records about associations between ants and hornets in Europe. In this study, we reported the first case of association between the arboreal ant Camponotus fallax and the European hornet Vespa crabro in Europe. The observations were made in Central Spain, where two colonies of C. fallax were found in two different avian nest-boxes inhabited by V. crabro when spotless starlings finished their breeding season. The reasons of this possible association are also discussed.