Faecal Sacs Research Articles

Discovery of interspecific alloparental care of silver-eared mesia nestlings by a mountain bulbul.

Although brood parasitism has been well documented among bird species, interspecific alloparenting, which is parenting behavior of adult individuals of one species toward the progeny of another species, is increasingly being reported. However, compared with the many reports of interspecific alloparenting behavior in North America and Europe, this phenomenon is less well known in China, with only two prior cases of interspecific alloparenting behavior in birds having been recorded. On June 23, 2022, we observed an instance of interspecific alloparental care provided by a mountain bulbul (Ixos mcclellandii) towards silver-eared mesia (Leiothrix argentauris) nestlings in Caihu Village, Jingdong County, Yunnan Province, southwestern China. We recorded 19.5 h of footage during the period in which the mountain bulbul provided care for the nestlings with the aim of documenting detailed observations of interspecific alloparenting to contribute to our overall understanding of this behavior. The alloparenting behavior of the mountain bulbul lasted for at least 5 days. During this period, both silver-eared mesia parents fed their nestlings 157 times and removed their nestlings' fecal sacs 5 times, while the mountain bulbul fed the nestlings 30 times and removed the nestlings' fecal sacs 4 times. In addition, the male silver-eared mesia parent chased the mountain bulbul away during nestling feeding. As there was no life history information for the mountain bulbul at that time, we were unable to directly determine why it exhibited interspecific alloparental care. Regardless of the reason for the mountain bulbul's behavior, these findings provide valuable information for future studies on the reproductive ecology of these two bird species.

Microfibers in the Diet of a Highly Aerial Bird, the Common Swift Apus apus.

Microplastic pollution is a pervasive global issue affecting various ecosystems. Despite the escalating production and well-documented contamination in both aquatic and terrestrial environments, the research focused on airborne microplastics and their interaction with terrestrial birds remains limited. In this study, we collected fecal sacs from Common swifts (Apus apus) to investigate their diet and to evaluate the potential ingestion of microplastics by both adults and nestlings. The diet was mainly composed of Hymenoptera and Coleoptera and did not differ among sexes and age classes. The 33% of nestlings' and 52% of adults' fecal sacs contained anthropogenic items, the totality of which was in the shape form of fibers. The 19.4% of the anthropogenic items were chemically characterized as microplastics, either polyethylene terephthalate (PET; two microfibers) or cellophane (four microfibers). Airborne anthropogenic items, including microplastic, might be passively ingested during the Common swift aerial feeding. In addition, our findings suggest that these ingested microparticles have the potential to be transferred to the offspring through food. While further research is essential to elucidate the pathways of microplastic ingestion, our results reinforce the evidence of the transfer of anthropogenic items from the atmosphere to the biota.

Diet composition of the Atlas Flycatcher Ficedula speculigera in Northeastern Algeria

Abstract The diet of the Atlas Flycatcher, an endemic bird species of North Africa is studied in Northeastern Algeria in the forest of Guerrouch in the Taza National Park. The diet analysis was based on the examination of the faecal sacs of the nestlings (n=150) collected in nest boxes installed in a mixed formation of Algerian oak and African oak (Quercus canariensis and Quercus afares). A total of 854 food items were identified, representing 49 prey taxa. The analysis of centesimal frequencies by class revealed the clear dominance of Insecta with 85.12%, followed by Arachnida 13.34%, Gastropoda 1.28% and Malacostraca 0.23%. Regarding orders, the diet was constituted mainly of Coleoptera 44.37%, followed by Hemiptera 21.89% and Araneae 13.34%. The size of the prey taxa varied between 3 and 14 mm with an average of 7.11±3.14 mm. The best represented size class was that which varies between 3 and 4.37 mm. To test the homogeneity between the 4 nest boxes sampled, an ANOVA test was applied. The results show the presence of 2 distinct groups of nesting boxes concerning the variable number of families / faecal sacs.

Potential prey and conservation implications of the Algerian Nuthatch Sitta ledanti (Vielliard 1976)

The Algerian Nuthatch ( Sitta ledanti), which is mentioned on the Red List of threatened species, is one of the first protected birds in Algeria. The species’ populations are distributed with low numbers in Babors’ Kabyliain northeastern Algeria. The diet composition of the species has been studied on a large scale in five large forests. The diet analysis method is based on the identification of the different prey items found in the fecal sacs of the nestlings. We divided the 89 identified prey into 81 insects, 7 arachnids and 1 gastropod, giving 88 arthropods and 1 mollusc. According to both the Cluster Dendrogram and the Costello graph, the Algerian Nuthatch becomes a specialist species while searching for prey to feed its nestlings. This supply of specific prey for nestlings has been observed in both evergreen (Atlas cedar or Algerian fir) and deciduous (Algerian or African oaks) forests. Only the relative abundances (RA) of each prey consumed, prey number per fecal sac, and prey diversity by forest type showed differences. The low proportion of gastropods found in the fecal sacs of Algerian Nuthatch nestlings may explain the low nutritional value of this prey or may also be due to its low abundance. The species’ nestlings consumed a lot of European Earwig ( Forficula auricularia) and White spotted rose beetle ( Oxythyrea funesta) which could be due to their high energy intake and abundance in the area near the nests. Repeated fires and other anthropogenic activity constitute direct threats to the species’ habitat, and its specialised diet on certain prey weakens the survival of this species with endangered conservation status.

Structural-functional changes in the proventriculus of poultry infected with transmissive viral proventriculitis

Transmissive viral proventriculitis (TVP) is a new avian disease, the etiology and pathogenesis and diagnostics of which remain unidentified, being therefore a subject of an active ongoing discussion among researchers and veterinary doctors. Cases of the disease have been reported and registered in many countries of the world. On poultry farms of Ukraine, this disease started to be diagnosed in 2019, according to the characteristic pathognomic changes. The article presents the results of pathoanatomical, histological and electronic-microscopical studies of the glandular part of the stomach of 62 ill broiler chickens aged 24-28 days and 7 clinical healthy broiler chickens of the same age. The samples of the proventriculus from the infected and clinically healthy chickens were fixated in 10% aqueous solution of neutral formalin and in 1.5% solution of glutaraldehyde in 0.2 molar cacodylate buffer (рН 7.2). Pathoanatomic necropsy of the infected broiler chickens revealed overall anemia, decrease in the volume of the spleen, thymus and fecal sac. In the glandular part of the stomach, the wall was slightly thickened, non-homogenously stained on the section, the mucous membrane being swollen, covered by dense whitish mucous. According to the histological study, the proventriculus of the broiler chickens had lymphocytic necrotizing proventriculitis. In the tubular-alveolar structures of the mucous membrane, there prevailed alteration of the secretory epithelium, with its transformation into ductal epithelium, combined with lymphocytic infiltration of the interstitium. Intensive necrosis of most glandular (oxynticopeptic) cells was accompanied by their exfoliation from the basal membrane of the secretory parts, with desquamated cells accumulating in enlarged lumens of alveoli and excretory ducts. Further, necrotized oxynticopeptic cells in the tubular-alveolar glands were actively replaced by cylindrical ductal cells, and also their hyperplasia and hypertrophy occurred. Diffusive and multifocal interalveolar round-cell infiltrates were mostly presented by lymphocytes, among which there occurred plasmocytes, macrophages, and heterophils. Ultrastructural studies of secretory cells revealed presence of pathogen virions in nucleus and cytoplasm. Based on the morphological changes in the birds’ proventriculus, we diagnosed transmissive viral proventriculitis, which had not been recorded in Ukraine before.

Double-broodedness, burial of faecal sacs and long breeding season in the Australian Logrunner in south-eastern Queensland

Observations of a female Australian Logrunner Orthonyx temminckii building a nest while feeding juveniles from a previous brood and, in the following year, incubating eggs while feeding a juvenile, represent the first documented evidence of multi-broodedness in this species. Consistent with the literature, incubation of eggs and feeding of nestlings were performed only by the female, which was fed frequently by the male when she was off the nest. Incubation attentiveness was 60%, and average incubation bouts were about twice the duration of absence bouts (44 vs 21 minutes) at one nest. Based on dates extrapolated from the date of fledging, brooding of the two nestlings ceased between Days 5 and 9. The hourly food-provisioning rate of nestlings increased linearly from 2.4 on Day 4 to 10 feeding visits on the day before fledging. Absence bouts during both the incubation and nestling period were apparently shorter, and food-provisioning rates substantially higher, than in the phylogenetically related Chowchilla O. spaldingii of Far North Queensland. Observations of the female Logrunner burying faecal sacs corroborate a previous observation in south-eastern Queensland and suggest a novel strategy to avoid attracting potential nest predators. Although the Logrunner is often thought to breed only in winter, records from multiple sources indicate that in Queensland >50% of clutches are laid during the rest of the year, presumably facilitated by year-round food availability.

New insights on the breeding biology of the Crow Honeyeater Gymnomyza aubryana suggest convergence with the Mao G. samoensis

Phylogenetic study of the honeyeater family shows that the four insular species of the genus Gymnomyza are polyphyletic, with the largest, the Crow Honeyeater G. aubryana, being a distinct and ancient lineage. The Critically Endangered Crow Honeyeater is a secretive species that lives in the rainforest of New Caledonia. For two breeding seasons (S1 in 2019 and S2 in 2020) we studied its breeding biology in the Parc Provincial de la Rivière Bleue. In S1, three nests (N1, N2, N3) were found and one nest (N4) in S2. Three dismantled nests (N1, N2 and N4) revealed four distinct layers; detailed measurements showed that Nest N2 consisted of 507 pieces of nest material and weighed 103 g. The female built the nest and incubated the one-egg clutch for 75% of time over a 24-hour period. The female rolled the egg each 33 minutes (n = 50) during the day and 118 minutes (n = 23) at night. The nest was 9.5 m above ground in a small tree (trunk 12 cm in diameter) and the trees and shrubs within 10 m mainly had trunks ⩽10 cm in diameter (n = 4). Laying occurred during the dry season (August–October). The feeding rate of the nestling was 2.6 times/h. Animal prey items accounted for 74.7% by number, of which 66.5% were orthopterans; indeterminate 9.7%, fruit 12.4% and only 3.2% was nectar (n = 1788). Prey items in the size range 21–40 mm in length constituted 59% of the nestlings’ food by number. The number of faecal sacs produced per nestling averaged 1.7/h (n = 956). The young fledged at 25.5 days (mean for two nests) and did not return to the nest, but was fed for another 2.6 months. One juvenile, from an unknown nest, remained at least 16.5 months in the adults’ territory. The home range of a male during 2.6 months (September to early December) was 24 ha. The Crow Honeyeater has a slow life history for breeding biology, as found also for the Mao G. samoensis. Both species evolved on tropical islands and show a convergent adaptation.

Diet and grit characteristics in young Eurasian Bullfinches (Pyrrhula pyrrhula) inhabiting Iberian hedgerows

For the first time, the diet of young Iberian Bullfinches (Pyrrhula pyrrhula iberiae) is studied, specifically in a hedgerow habitat in northwestern Spain, through stomach (younger nestlings up to 8 d of age, which died without researcher intervention) and faecal sac (older nestlings) analysis, and secondarily direct observation (nestlings and dependent juveniles). Also, for the first time, grit use by bullfinch nestlings is described in some detail. Bullfinches fed their young with a mixture of seeds and invertebrates, with greater quantitative importance of the former. The identity of the seeds varied considerably between spring and summer, and animal fraction gradually decreased from May to July for older nestlings, in both cases presumably because of the seasonal changes in food availability. Caterpillars and spiders were the most important arthropod prey in the diet. Apparently, the young were not fed non-arthropod invertebrates. The relative importance of invertebrates, which are very rich in proteins, was greater for younger nestlings than for older ones. Difficult to digest hard-bodied prey, such as beetles, were not present in the stomachs of the youngest nestlings. The frequency of occurrence and amount of grit in stomachs increased with nestling age, along with the need to grind food. There were no remarkable differences in number of units, size, or number of colour types of gastroliths between months. The high floristic diversity in the study area, which has great overall conservation value, provides a wide range of resources for bullfinches, including plenty of food for their young.

Egg Rejection and Nest Sanitation in an Island Population of Barn Swallows (Hirundo rustica): Probability, Response Latency, and Sex Effects.

Bird nests function as vessels for eggs and nestlings, and an environment for rearing offspring. However, foreign objects falling into bird nests and nestling eggshells may be harmful. Moreover, the smell of fecal sacs increases the risk of detection by predators. Many bird species have evolved nest sanitation to prevent damage to their nests. Furthermore, egg rejection evolved in some birds to thwart brood parasites that lay eggs in their nests. We studied 133 nests of barn swallows (Hirundo rustica) in an island population through a nest content manipulation experiment to determine nest sanitation and egg rejection behaviors and their relationship. Swallows rejected non-egg foreign objects more frequently (100% vs. 58.6%) and sooner than parasite eggs, which supports the hypothesis that nest sanitation is a pre-adaptation to egg rejection. However, nest sanitation did not increase egg rejection, either in probability or latency. Furthermore, both sexes incubated the eggs, cleaned the nests, and removed parasite eggs, implying that both are confronted with natural selection related to nest sanitation and brood parasitism. However, females invested more time in these behaviors than males. This provides evidence for the evolutionary relationship of nest sanitation and egg rejection behaviors in barn swallows.

Another Example of Nest Sharing by American Robins and Gray Catbirds

In June 2020, we monitored a nest in Southampton, MA, that contained 2 Dumetella carolinensis (Gray Catbird) and 3 Turdus migratorius (American Robin) eggs. Females of both species alternately incubated the mixed clutch, and 2 catbird and 2 robin young successfully hatched and fledged from the nest. Adults of both species provided both intra- and interspecific parental care (e.g., nestling provisioning, brooding, and nest sanitation). The catbirds, in particular, often did not preferentially provision their own young. In fact, following earlier fledging of the catbird young, an adult catbird continued to visit the nest to care for the robin nestlings, including fecal sac removal on at least 2 occasions. After the 2 robin young fledged, we did not observe any crossover post-fledging care. Our study represents the most detailed and protracted account among the very few documented cases of nest sharing between these species.

A comparison of fecal sac removal rates of male and female Carolina Chickadees (Poecile carolinensis)

Parent songbirds keep their nests clean by removing nestling waste in the form of fecal sacs. Removing fecal sacs is beneficial for the nestlings but energetically costly for the parents. The purpose of our research was to determine whether there was a difference in energy spent on fecal sac removal between male and female Carolina Chickadees (Poecile carolinensis). We collected data for this project at St. Anne Woods and Wetlands in Melbourne, Kentucky, where we made a total of 215 one-hour observations of 30 different nests. For each color-banded parent, we calculated both the number of fecal sac removals and the number of removals divided by the total number of nest visits per hour. Our results showed that males removed more fecal sacs per hour than females. However, this was only because they visited the nest more frequently, as the number of fecal sac removal visits per provisioning visit was the same between the sexes. This suggests that parental energy invested in fecal sac removal is closely tied to their investment in nestling provisioning visits.

Breeding biology of the White-winged Robin Peneothello sigillata, endemic to montane New Guinea

I studied the breeding biology of the high-elevation montane White-winged Robin Peneothello sigillata (Petroicidae) at Kumul Lodge, southern slope of Mt Hagen, Papua New Guinea, from 2 October to 17 November 2011. Three nests were watched for 18 hours during incubation; each had one egg. Female daylight incubation constancy (percentage of daylight hours spent in incubation) was 73%, the mean duration of incubation sessions was 3.35 minutes and mean absence from the nest was 1.33 minutes, the daily number of incubation sessions was 150 (12.5 per hour), feeding of the incubating female by the male at the nest was 4.6 times/hour, and the total number of nest visits by both male and female during incubation was 17.1/hour. The 100% egg-success in this species suggests that these incubation reproductive traits evolved more in response to food availability and perhaps food limitation than a high risk of nest predation. Nestling care by the female included brooding and the feeding of the young. Nestling care by males included delivering food to the female and feeding the nestling. Both the male and the female removed faecal sacs. Mean brooding constancy (percentage of time spent brooding) was 43.3% for the entire 17–21-day nestling period. Mean number of food-delivery trips by both the male and the female over the entire nestling period was 7.2/hour/nestling and the total number of nest visits by both the male and the female was 17.6/hour. Two nests were attended solely by the breeding pairs, and cooperative breeding, with one immature helper, occurred at one other nest. During the nestling stage, the high nest success, coupled with high nest visitation, suggests that the risk of nest predation is low. Peak nestling growth (to >90% of adult weight) occurred at 10–13 days of age. To elucidate the breeding strategy of the White-winged Robin, its reproductive traits are discussed and compared with those of other robins of New Guinea, tropical northern Australia, and temperate Australia and New Zealand.

Interspecific parental care by a European Starling (Sturnus vulgaris) at the nest of a Hairy Woodpecker (Dryobates villosus)

The European Starling (Sturnus vulgaris) is a cavity-nesting species that aggressively competes with other cavity nesters, such as woodpeckers, and usurps their nest cavities. Interspecific parental care among birds is uncommon and scarcely reported for European Starlings and woodpeckers. Here, we report an observation of a clutch of 3 Hairy Woodpecker (Dryobates villosus) nestlings being fed by both an adult female Hairy Woodpecker and at least 1 adult European Starling in southern Ontario, Canada. There are differences in parental behavior observed between the starling and female Hairy Woodpecker, namely only the starling entered the cavity (7.0 times/h) and removed fecal sacs (4.2 times/h) while the female Hairy Woodpecker never showed these behaviors during our observation period, but she fed nestlings 7.4 times/h compared to 4.9 times/h by the starling. Although proximate causes of this behavior are unclear, nest site competition, overlap of the timing of breeding and preferred habitat, or the loss of the male woodpecker may have triggered this behavior.

The potential of aerial insectivores for monitoring microplastics in terrestrial environments

Limited research has been conducted on microplastics in terrestrial ecosystems and biota, despite being some of the most ubiquitous environmental pollutants. We investigated the presence of microplastics (over 125 μm) in tree swallow (Tachicyneta bicolor) chicks (10 d. o.), an aerial insectivore whose diet involves terrestrial and/or freshwater sources. Swallows nested immediately downstream (300 m) of the discharge pipe of a large, urban wastewater treatment plant (WWTP) or at a rural conservation area (40 km apart). Anthropogenic microparticles (including microplastics) were identified in nearly all WWTP chicks (90%; N = 20) and reference chicks (83%; N = 20). All microparticles were fibers (100%) in the gastro-intestinal (GI) tracts of WWTP nestlings, whereas unexpectedly, they were more diverse in the GI tracts of reference chicks, with ~15% characterized as pre-production plastic pellets. The fecal sacs of most nestlings (90%) contained microparticles, and all were characterized as fibers suggesting their excretion by tree swallows. Compared to WWTP chicks, the reference chicks had more microparticles in their fecal sacs and larger particles (length, width) in their GI tracts, likely reflecting the more aquatic-based diet of the reference chicks fed insects caught adjacent to the nearby dam, compared to the more terrestrial-based diet of the WWTP chicks. The numbers of microparticles were not correlated between GI tracts and fecal sacs, nor with the chicks' condition or size (weight, organs, feathers). We recommend sampling macroinvertebrate prey to permit stronger conclusions regarding WWTPs as possible sources of microplastics for swallows, and to determine if such macroinvertebrates may be a non-lethal method to characterize microparticle diversity ingested by birds as presently identified in chicks' GI tracts. We conclude that sampling fecal sacs only, while not indicative of the diversity of microplastics ingested by terrestrial passerines (e.g., tree swallows), is useful for determining their exposure to microparticles.

Task division in a facultative cooperative breeder bird: do males take out the trash?

Abstract Cooperative animals share different activities during reproduction, but individuals of a social group may invest in these tasks in different proportions. Nest sanitation is an important task that may impact reproductive performance of birds, and yet, little is known about the relative participation of individuals of a social group, particularly in non-passerine species. Here, we describe nest sanitation behaviour and materials removed, and test the occurrence of task division regarding faecal sac removal in Campo flickers (Picidae), a facultative cooperative breeder with complex social system. We found that helpers removed proportionally more faecal sacs than breeders, and male helpers are mainly responsible for this activity. These results are different than the commonly reported patterns for passerines, where females are the main contributors. Different ecological conditions and benefits achieved by group members may influence their investment in nest sanitation, but additional studies on social species could greatly contribute to our understanding of how general our results are in non-passerine species.

OBSERVATIONS ON THE PARENTAL CARE OF THE YELLOW-BELLIED ELAENIA Elaenia flavogaster subpagana

We observed three nests of Yellow-bellied Elaenia Elaenia flavogaster subpagana in La Selva, Costa Rica. One nest had a single nestling, which was observed for 21 h in order to document incubation, breeding and feeding behaviors. We quantified number of visits per h to the nestling, as well as food transfer events and fecal sac removal, and confirmed that two parents fed the nestling. Adults visited the nest 4.9 ± 0.6/h/nestling on average. We observed 18 feeding events between adults, and five food transfer episodes of the incoming adult to the incubating adult, and then to the nestling. Food items brought to the nest included Diptera, Coleoptera, Phasmatodea, Hymenoptera, Araneae and berries.

Breeding biology of the Creamy-bellied Thrush (Turdus amaurochalinus) in southeast Brazil

ABSTRACT The description of life-history traits is a prerequisite to understand the complex patterns of bird biodiversity. However, most of the highly diverse Neotropical avifauna still lack basic information on their reproductive behavior. Here, we describe the breeding biology of the Creamy-bellied Thrush (Turdus amaurochalinus) in a periurban area of southeast Brazil. We found 67 nests between early September and December in 2017 and 2018. Nests were 3.8 ± 1.9 m (mean ± SD) above ground, in native plants (43.3%), exotic plants (43.3%), and anthropogenic structures (13.4%). Clutch size was 2.9 ± 0.3 eggs, which were incubated exclusively by females during 75.6 ± 18.1% of the time. Both sexes reared the nestlings, but females performed more feeding trips and removed more fecal sacs than males. Incubation and nestling periods lasted, respectively, 13.0 ± 0.6 and 13.2 ± 1.5 days. Overall nesting success according to Mayfield method was 31.6%, and predation was the major cause of nest failure (52.8%). We concluded that this species had higher nest attentiveness, shorter nestling period, and higher nest survival compared to other Neotropical thrushes. The use of exotic plants and anthropogenic structures as nesting substrate may enhance the settlement of this migratory thrush in human-modified areas.

Breeding biology of the Sayaca Tanager (Thraupis sayaca) in southeast Brazil

ABSTRACTThraupis is a genus of the American endemic Thraupidae (subfamily Thraupinae), comprising seven species that inhabit tropical forests to urban centres. The Sayaca Tanager (Thraupis sayaca) is a disturbance-tolerant species of high representativeness in plant-frugivore networks, but information on its breeding biology is scarce and often restricted to non-systematic surveys. We studied the breeding biology of the T. sayaca, following 39 active nests in a periurban area of southeast Brazil during two breeding seasons (2017/2018, 2018/2019). The breeding season ranged from early September to middle December, and the nests were placed in native and exotic plants and human buildings (nest height above ground: 3.35 ± 1.73 m, mean ± SD). Only females incubated and brooded, but both adults built the nests, fed the nestlings, and removed their faecal sacs. Clutch size was 2.86 ± 0.38 eggs and nest attentiveness was 71.2%. The incubation and nestling periods were, respectively, 13.4 and 17.4 days. Males and females did not differ on nestling provisioning and nest sanitation rates. Nestling provisioning (13.35 ± 6.25 trips/hour) increased with nestling age, while mean brooding time was 37.2% and decreased with nestling age. Apparent nest success was 38.7%, and nest survival according to the Mayfield method was 27.2%. Five nests (20.8%) were parasitised by the Shiny cowbird (Molothrus bonariensis), and we recorded five events of nest-site reuse. We concluded that the most remarkable breeding traits of T. sayaca in comparison with close-related tanagers are the use of anthropogenic nest sites, the higher clutch size and number of feeding trips, and the longer nestling period.

Poecile atricapillus (Black-capped Chickadee) Feeding Catharus guttatus (Hermit Thrush) Nestlings

We describe what we believe to be the first recorded instance of an adult Poecile atricapillus (Black-capped Chickadee) feeding the young of a different species. On 25 June 2017, we observed a Black-capped Chickadee feeding 3 Catharus guttatus (Hermit Thrush) nestlings. We recorded a video of this behavior the following day, in which the adult Black-capped Chickadee delivered food to the Hermit Thrush nestlings 12 times in 105 min of continuous recording. The Black-capped Chickadee also removed fecal sacs from the nest. At the end of this video, 1 of the nestlings fledged. We did not observe an adult Hermit Thrush feeding the nestlings during the entire recording. The considerable differences in body size, nesting strategy, and nestling growth rate between these 2 species comprise a unique instance of interspecific parental feeding that resulted in successful fledging.

Experimentally broken faecal sacs affect nest bacterial environment, development and survival of spotless starling nestlings

Nestlings of most avian species produce faecal sacs, which facilitate the removal of nestlings’ excrements by parents, thereby reducing proliferation of potentially pathogenic microorganisms and/or detectability by predators and parasites. The nest microbial environment that birds experience during early life might also affect their development and thus, faecal sacs facilitating parental removal may be a strategy to decrease bacterial contamination of nests that could harm developing nestlings. Here, we tested this hypothesis by experimentally broken faecal sacs and spreading them in nests of spotless starlings Sturnus unicolor, thereby avoiding their removal by adults. In accordance with the hypothesis, experimental nests harboured higher bacterial density than control nests. Nestlings in experimental nests were of smaller size (tarsus length) and experienced lower probability of survival (predation) than those in control nests. Moreover, nestlings in experimental nests tended to suffer more from ectoparasites than those in control nests. We discuss the possible pivotal role of bacteria producing chemical volatiles that ectoparasites and predators might use to find avian nests, and that could explain our experimental results in starlings.