Reproductive Success Of Birds Research Articles

IMPACTS OF INTENSIVE AGRICULTURE ON BIRDS: A REVIEW

Intensive agriculture has had a negative impact on biodiversity and human health across the world. Specifically, bird populations have declined for many years due to soil degradation and agrochemical pollution. This review, which draws on 890 sources, including research articles and literature reviews, examines the interaction between birds and intensive agriculture to better understand its effects and conservation implications. Intensive agricultural activities have resulted in significant population declines among insectivorous and carnivorous birds, while generalist bird populations have increased. The heavy use of pesticides in intensive agriculture affects food availability for birds by reducing invertebrate and vertebrate populations as well as natural vegetation cover, which has a significant impact on bird diversity. Additionally, the accumulation of toxic compounds reduces bird reproductive success. In general, intensive agroecosystems have consistently had lower avian diversity than forest habitats and even lower-impact agricultural systems. However, some agroecosystems, such as rice fields, agricultural drainages, and canal systems, create alternative habitats that can benefit waterfowl. Future work should consider strategies such as restoring and enhancing vegetation edges, preserving natural vegetation, implementing organic farming practices, maintaining water bodies, and providing economic incentives for landowners to conserve biodiversity on their land to promote bird diversity conservation.

A global database of bird nest traits

The reproductive success of birds is closely tied to the characteristics of their nests. It is crucial to understand the distribution of nest traits across phylogenetic and geographic dimensions to gain insight into bird evolution and adaptation. Despite the extensive historical documentation on breeding behavior, a structured dataset describing bird nest characteristics has been lacking. To address this gap, we have compiled a comprehensive dataset that characterizes three ecologically and evolutionarily significant nest traits—site, structure, and attachment—for 9,248 bird species, representing all 36 orders and 241 out of the 244 families. By defining seven sites, seven structures, and four attachment types, we have systematically classified the nests of each species using information from text descriptions, photos, and videos sourced from online databases and literature. This nest traits dataset serves as a valuable addition to the existing body of morphological and ecological trait data for bird species, providing a useful resource for a wide range of avian macroecological and macroevolutionary research.

Potential impacts of land‐management schedules on grassland bird nests and fledglings

AbstractTrade‐offs exist between timing of grassland habitat management activities (e.g., weed and brush control) while also ensuring other conservation objectives (e.g., grassland bird reproductive success) are met. On land set aside for grassland conservation (e.g., lands enrolled in the U.S. Department of Agriculture Conservation Reserve Program and some state and federal wildlife management areas), federal and state agencies set time frames for land management based on avoiding disturbance of grassland bird nests. However, recent calls for considering the needs of dependent fledglings in conservation plans imply a need to evaluate whether current time frames are adequate. We used initiation and end dates for 3,257 nests of 8 obligate grassland bird species in Illinois and Wisconsin and a simulation approach for fledgling survival to estimate the potential proportion of active nests at risk when management (e.g., mowing, fire) occurred on the 1st and 15th day of May, June, July, and August during the breeding season. Management during June had the potential to impact 24–61% of nests, depending on the species. Management during July had the potential to impact 4–52% of nests, depending on the species. If disturbance occurred during August, proportionately few active nests were at risk for any species (0–9% of nests on 1 August, 0–<0.5% on 15 August). Potential proportions of fledglings at risk from management were greatest in July for 7 of the 8 species (7–18%). Our study suggests that on lands where a primary conservation objective is to increase or ensure survival of grassland birds, delaying management activities until August could be beneficial for protecting both grassland bird nests and fledglings.

Effects of conventional vs. organic farming practices on raptor nestling health: Neither black nor white

Agricultural intensification is one of the main threats to biodiversity. Farmland bird specialists such as Montagu’s harrier, Circus pygargus, are particularly at risk and declining. Conventional farming (CF) production systems usually involve landscape homogenisation, mechanisation, and the use of synthetic pesticides that may have direct and indirect effects on individuals. By contrast, organic farming (OF) systems typically promote agro-ecosystem health, which benefits biodiversity and the reproductive success of birds. However, the potential effects of agricultural systems on life history traits of Montagu’s harrier chicks have not been investigated. Still, altered life history traits could impair chick survival and future reproductive success, which may in turn impact population dynamics. Here, we investigated the effects of OF (measured as a percentage around nests at different buffer sizes from 100 m to 2000 m) on a set of life history traits covering the behaviour, physiology (haematological, immune and nervous systems) and body condition of 380 chicks from 137 nests monitored between 2016 and 2021. At a local scale (<2000 m), only the H/L ratio (indicative of physiological stress) and carotenoid-based ornaments were clearly related to OF percentage. At 600 m around the nest, a higher OF percentage increased the H/L ratio, suggesting that chicks experienced greater stress due to either increased human disturbance or higher intra-/interspecific negative interactions around OF crop plots. Carotenoid-based ornaments were more strongly coloured with increasing OF around the nest at 1500 m. Considering the role of carotenoids in both detoxification processes and expression of secondary sexual traits, this result may indicate that CF would lead either to a difference in nestlings’ diet and/or to a trade-off between organism’s maintenance and sexual characters. These findings suggest that farming practices at a local scale surrounding nest locations may have subtle effects on chick development, but also on trade-offs between important physiological functions. This study highlights the importance of a multi-trait approach when assessing adverse and beneficial effects of both OF and CF on individuals.

To Prevent Oxidative Stress, What about Protoporphyrin IX, Biliverdin, and Bilirubin?

The pigments responsible for eggshell color and patterning in birds are protoporphyrin IX (PP) and biliverdin (BV). Both are involved in the catalytic degradation of the hemo group. Bilirubin (BR), another pigment, is produced when BV is broken down. PP, BV, and BR are free radical scavengers. In this study, we theoretically investigated the antioxidant capacities of these three biological meaningful molecules using Density Functional Theory calculations. First, two antioxidant mechanisms were analyzed for PP, BV, and BR: electron transfer and Hydrogen Atom Transfer. Second, since PP and BV interact with the calcium carbonate matrix of the eggshell, we analyzed the interaction of these pigments with Ca2+ and investigated their chelate compounds. Third, we explored the pro-oxidant properties of PP and BV, which have been proposed for PP when photoactivated to the triplet state, but not for BV. Our results show that PP, BV, and BR are just as good antiradical as other important natural pigments (carotenoids). Neither the antiradical properties of PP and BV nor the UV-visible spectra change due to the presence of calcium, suggesting that the signaling function of these pigments is not affected by the link with Ca2+. Finally, we found that both PP and BV (alone and when linked to Ca2+) can transfer energy from its triplet state to molecular-oxygen-producing singlet oxygen, indicating their pro-oxidant capacity. This investigation answers important questions about the function of these pigments, which may help to understand their influence on the reproductive success of birds.

Consequences of arthropod community structure for an at-risk insectivorous bird.

Global declines in bird and arthropod abundance highlights the importance of understanding the role of food limitation and arthropod community composition for the performance of insectivorous birds. In this study, we link data on nestling diet, arthropod availability and nesting performance for the Coastal Cactus Wren (Campylorhynchus brunneicapillus sandiegensis), an at-risk insectivorous bird native to coastal southern California and Baja Mexico. We used DNA metabarcoding to characterize nestling diets and monitored 8 bird territories over two years to assess the relationship between arthropod and vegetation community composition and bird reproductive success. We document a discordance between consumed prey and arthropod biomass within nesting territories, in which Diptera and Lepidoptera were the most frequently consumed prey taxa but were relatively rare in the environment. In contrast other Orders (e.g., Hemiptera, Hymenoptera)were abundant in the environment but were absent from nestling diets. Accordingly, variation in bird reproductive success among territories was positively related to the relative abundance of Lepidoptera (but not Diptera), which were most abundant on 2 shrub species (Eriogonum fasciculatum, Sambucus nigra) of the 9 habitat elements characterized (8 dominant plant species and bare ground). Bird reproductive success was in turn negatively related to two invasive arthropods whose abundance was not associated with preferred bird prey, but instead possibly acted through harassment (Linepithema humile; Argentine ants) and parasite transmission or low nutritional quality (Armadillidium vulgare; "pill-bug"). These results demonstrate how multiple aspects of arthropod community structure can influence bird performance through complementary mechanisms, and the importance of managing for arthropods in bird conservation efforts.

Beyond habitat: effects of conspecific and heterospecific aggregation on the spatial structure of a wetland nesting bird community

Nest location is a key factor influencing reproductive success in birds, and habitat choice is considered the main way in which birds select nest sites. Less attention has been devoted to the demand for proximity to other bird nests, which can provide additional profit, namely defense against predators. Here we analyzed the contributions of habitat, and conspecific and heterospecific aggregation to the spatial arrangement of breeding birds in a model bird community. We surveyed a pristine Siberian wetland bird community with the aim to locate all bird territories or nests, in 1993 and 2013. Habitat explained much of the nest site choice, but the nests were aggregated both intra‐ and inter‐specifically more than the spatial pattern of the habitat could explain. In particular, ducks, grebes and some waders bred nearby the most abundant active nest defenders, such as gulls and terns. Heterospecific associations were particularly pronounced in 2013, when the community was impoverished and one common active defender (white‐winged black tern Chlidonias leucopterus) was replaced by a less numerous but aggressive predator (Mongolian gull Larus mongolicus). The results suggest that spatial pattern in bird nests may be influenced by the (dis)appearance of one or a few species, which can play a role as umbrella or predator species. Integration of factors supporting the breeding of umbrella species, such as gulls, may became key targets for comprehensive conservation measures in large wetlands.

Multifaceted roles of the egg perivitelline layer in avian reproduction: Functional insights from the proteomes of chicken egg inner and outer sublayers

The avian egg perivitelline layer (PL) is a proteinaceous structure that encloses the egg yolk. It consists of the inner and the outer perivitelline layers (IPL and OPL, respectively) that are assumed to play distinct roles in bird reproduction. To gain insight into their respective function, we analyzed the proteome of IPL and OPL in chicken unfertilized eggs after mechanical separation, using a GeLC-MS/MS strategy. Of the 412 proteins identified, 173 proteins were uniquely recovered in IPL and 98 proteins in OPL, while 141 proteins were identified in both sublayers. Genes coding the most abundant proteins were shown to be expressed either in the liver/ovary (IPL formation) or in the oviduct (OPL formation), but rarely in both. The presence of oviduct-specific proteins (including LYZ, VMO1, AvBD11, PTN, OVAL and LOC10175704) in IPL strongly suggests that they participate in the physical association of IPL to OPL, whose tight attachment was further evidenced by analyses of IPL/OPL interfaces (by scanning electron microscopy). Functional annotation of identified proteins revealed functions associated with fertilization and early development for IPL, while OPL would rather participate in egg defense and embryogenesis. Collectively, our data highlight the complementary functions of IPL and OPL that are major determinants of bird reproductive success. SignificanceThe present study unveils for the first time the individual proteomes of the two sublayers composing the chicken egg perivitelline layer (PL), which allowed to assign their respective putative biological roles in avian reproduction. The combination of proteomics with gene expression and ultrastructural analyses provides insightful data on the structure and biochemistry of the avian PL. The functional annotation of PL proteins highlights the multifaceted biological functions of this structure in reproduction including fertilization, embryonic development, and antimicrobial protection. This work will stimulate further research to validate predicted functions and to compare the physiology and the functional specificities of PL in egg-laying species.

Large-scale supplemental feeding alters lay date and nest survival in Eastern Bluebirds but not in two species of chickadees

Abstract Wild bird feeding is a popular and growing activity, with approximately half of households participating in nations including the United States, Canada, the United Kingdom, New Zealand, and Australia. Supplemental feeding can increase survival and reproductive success of birds (which is often a goal of supplemental feeding efforts), but it raises concerns about phenological mismatch and possible increased risk of nest predation. Our objectives were to test whether access to supplemental food during the breeding season was correlated with (1) advanced egg-laying phenology, (2) increased clutch size, or (3) improved nest survival of 3 cavity-nesting species (Carolina Chickadee [Poecile carolinensis], Black-capped Chickadee [P. atricapillus], and Eastern Bluebird [Sialia sialis]) at a large spatial scale (the United States and Canada; spanning 22° latitude and 55° longitude). We examined data from 24,528 nest attempts submitted to NestWatch from 2014 to 2019. For Eastern Bluebirds, birds with access to supplemental insects initiated clutches 5.83 ± 0.89 (mean ± SE) days earlier than birds without access to food subsidies, whereas predicted nest survival was 5% greater for birds with access to supplemental insects (probability of nest success = 0.79, 95% CI: 0.77–0.81) than for birds without (0.74, 95% CI: 0.72–0.75). Clutch size of Eastern Bluebirds did not differ between birds with and without access to supplemental insects. For chickadees, supplemental feeding (of seeds, suet, insects, or fruit) was not correlated with phenology, clutch size, or nest survival. Our results suggest that supplemental feeding of insects can be an effective tool for increasing nest survival in Eastern Bluebirds and potentially other food-limited insectivores. However, the efficacy of supplemental feeding for improving reproductive success varies across taxa, likely related to diet. Despite widespread feeding of Black-capped and Carolina Chickadees, supplemental food had no discernable effect on timing of egg-laying, clutch size, or nest survival.

Impact of extreme environmental conditions: Foraging behaviour and trophic ecology responses of a diving seabird, the common diving petrel

The reproductive success of birds is strongly driven by environmental conditions at different time scales. Thus, during periods of low food availability, breeding success is constrained by the ability of adults to adapt their foraging effort and feeding behaviour to maintain regular incubation shifts and chick provisioning. However, while large seabirds can buffer disruptions in prey availability, the ecophysiological constraints of smaller species may limit their behavioural flexibility. By combining information on at-sea movements, foraging habitat, trophic niche, and breeding success, this study evaluated the effects of intense variability in oceanographic conditions on common diving petrels (Pelecanoides urinatrix) at the northern extent of their range in south-eastern Australia during four consecutive breeding seasons. Unusually low breeding success (6 and 0%) was observed during two years with intense heatwave events, which were associated with higher foraging effort (foraging trips twice longer) and a substantial shift in trophic niche (lower blood δ15N values). These findings suggest that common diving petrels in Bass Strait may have reached a critical threshold above which buffering the effects of environmental variability on their reproductive output is not possible. The clear cascading impacts that marine heatwaves have on zooplankton feeders illustrate the profound bottom-up effect induced by such extreme environmental variations, and suggest strong impact on higher-trophic levels. The wide, circumpolar breeding distribution of the common diving petrel, and its high sensitivity to variations in oceanographic conditions, suggest that this species may be a suitable model to study short-term and long-term behavioural responses to the effects of climate change throughout the Southern Ocean.

Head and body orientation of the White Stork Ciconia ciconia during incubation: effect of wind, apex predators and power lines

Incubation behaviour is essential for understanding the reproductive success in birds. For example, the orientation of the bird is important for reducing incubation costs associated with wind or sun, but on the other hand can be modified by the perceived risk of predation. We studied the body position of incubating White Stork Ciconia ciconia in eastern Poland using a small unmanned aerial vehicle (drone). The head and body orientation of the incubating storks was non-random and modified by natural factors, mainly wind direction and speed, but also by the presence of an apex predator, the White-tailed Eagle Haliaeetus albicilla. However, head orientation during incubation in nests located on electricity poles was also modified by the presence of the power lines, probably due to disturbance in the magnetic field detected by birds. Surprisingly, although the positioning of incubating birds (mainly females) is very important for the detection of predators and for reducing energy costs, these have not previously been studied. New technologies, such as drones, make it possible to collect new, extensive information on the incubation behaviour of birds.

Eggshell consumption in different reproductive stages and broods of the Western Bluebird, Sialia mexicana

Calcium is an essential micronutrient to egg production and reproductive success in birds. Its availability at the start of the reproductive cycle is especially important to passerines (perching birds, namely songbirds) since they do not store calcium when not reproducing. To date, no data has been published to illustrate whether Western Bluebirds would consume provisioned eggshells, during which phases and to what degree in the reproductive cycle consumption might occur, and whether the amount consumed would vary between broods in a single season. We hypothesized that Western Bluebirds would consume the highest amount of eggshells during nest-building and egg-laying and that consumption would be greater during the first brood. Western Bluebirds breeding in nest boxes hanging in trees were provided eggshells in small containers attached to the roof of the box. Differences in average consumption between reproductive stages were significant. The greatest consumption was seen during the Pre-hatch phase (nest-building, egg-laying, and incubation), and less during the Post-hatch phase (nestling and fledgling). This was likely in preparation for and to replenish calcium needed during egg-laying in both broods. Average consumption between two broods produced by a single breeding pair was not significantly different. However, there was significant variation in the amount of consumption between breeding pairs. This high variation suggests that birds may have different strategies for obtaining and consuming calcium.

Incubation in a Temperate Passerine: Do Environmental Conditions Affect Incubation Period Duration and Hatching Success?

The timing of breeding often has a profound influence on reproductive success in birds living in seasonal environments in which nestling food availability changes rapidly. Timing is typically investigated with reference to lay dates, but the timing of hatching is also influenced by the length of the incubation period, which is likely to depend on both environmental conditions and parental behaviour. The aim of this study was to use a 24-year dataset to investigate the abiotic and biotic factors influencing variation in incubation duration in long-tailed tits (Aegithalos caudatus), a species exhibiting substantial variation in incubation duration. We also assess the consequences of variation in the length of incubation periods for hatching success and the risk of nest predation. We found support for our predictions that later breeding attempts, drier conditions and larger clutches were associated with shorter incubation periods. Larger clutches were also more resilient to increases in incubation duration associated with rainy conditions. Surprisingly, warmer ambient conditions were associated with longer incubation periods. Weather conditions did not influence hatching success suggesting that adverse conditions are buffered by nests or by parental behaviour. We also show that longer incubation periods are likely to be costly, however, due to increased exposure to nest predators, and because longer incubations are associated (albeit weakly) with increased risk of hatching failure.

Greenfinches nesting in algerian orchards delayed their breeding and produced less fledglings in the driest of two years

The matching of breeding with the food peak is one of the most important factors affecting the reproductive success in birds. Weather is known to affect the timing of breeding of many bird species. In arid lands, rainfall is usually the factor that triggers the onset of reproduction, since it commonly anticipates the peak of food through its influence on the vegetation development. In this study we used a granivorous finch (European greenfinch Chloris chloris) as a model to assess the influence of rainfall and temperature on the onset and performance of breeding. The study was carried out in fruit orchards in Guelma state (Northeastern Algeria) in 2013 and 2014. The comparison of breeding parameters between the two years showed that greenfinches delayed their breeding in the year that the rains fell later and were less abundant, produced smaller broods and had lower fledgling rate. Clutch size decreased with the season progress only this year. We discuss our results in the context of the influence of weather on bird reproduction in arid lands, while providing novel data on a farmland species from a region with little ornithological information.

First Record of Total Leucism in the Clay-colored Thrush (Turdus grayi, Aves, Passeriformes, Turdidae)

We present the first record of total leucism for the Clay-colored Thrush, Turdus grayi, and the fourth case of chromatic aberration for this species. From April 2019 to August 2020, we observed an adult individual characterized by a lack of pigmentation with completely white plumage and eyes of normal color. The locality of occurrence corresponds to the tropical humid forest of the Lancetilla Botanical Garden, 250 meters from the city of Tela, on the north coast of Honduras. Documenting these cases in the Neotropical region is important to better understand pigment abnormalities, and studies are necessary to evaluate the survival and reproductive success of birds that present a lack of pigmentation.

Nests built on power lines: Nest-site selection by long-tailed broadbills (Psarisomus dalhousiae) in Nonggang of Guangxi, China

The quality of breeding habitat may directly affect the survival and development of progeny. Therefore, the selection of a suitable nest-site is an important factor affecting the reproductive success of birds. The most important reason for a bird’s reproductive failure is nest predation. Predation may cause birds to change their nest-sites and even nest morphology. Here we investigated the nest-site characteristics by long-tailed broadbills ( Psarisomus dalhousiae) in Nonggang, Guangxi, southwestern China. Our results showed that long-tailed broadbills in Nonggang mainly build their nests on power lines (88.5%) and nest-site selection was mainly affected by predation pressure and food resources. At the same time, nest-site concealment was trade-off against predator avoidance. This anti-predator strategy effectively utilizes human infrastructure.

Snakes are the principal nest predators of the threatened reed parrotbill in a coastal wetland of eastern China

Nest predation is a major limiting factor of bird reproductive success, and predation by snakes may have particularly adverse effects on passerines. The reed parrotbill (Paradoxornis heudei) is a threatened passerine that inhabits reedbeds in East China, where it faces the risk of population decline due to habitat loss and degradation. Studies on the nest predation of this species are lacking. In this study, we monitored reed parrotbill nests in the core area of the Yancheng Nature Reserve, Jiangsu Province, China. We tracked the final fate of each nest and determined the identity of the predators using infrared cameras. We monitored a total of 13 and 15 active nests in 2017 and 2019, respectively, but only 5 nests were successful. Nest predation was responsible for 22 of 23 nest failures (95.7%). Snakes were the principal predators of the nests, responsible for 19 predation events (86.4%). We used abandoned reed parrotbill nests and quail eggs to create artificial nests. However, the survival rate of the artificial nests (63.3%) was significantly higher than that of the natural nests (11.3%), and rats replaced snakes as the principal predators. The best model indicated that the daily survival rate of reed parrotbill nests decreased with nest age. Our findings suggest that severe snake predation may be an important factor threatening populations of the reed parrotbill, even though the wetland habitat is well protected. The identification of specific nest predators may facilitate the conservation of this near-threatened bird through the development of effective management strategies in reserves. More studies on population estimates of the reed parrotbill and the interactions between this endangered bird and snakes using natural (rather than artificial) nests in different areas are needed.

Thrush anvils are calcium source hotspots for many bird species

Abstract Calcium is one of the most important elements determining reproductive success in birds, and snail shells are a well-known source of calcium for egg-laying females. In Europe, song thrushes, Turdus philomelos, break snails open at locations called anvils, eat the soft parts and leave the broken shells. Based on observational studies in 2011–2017 in western Poland, we showed that thrush anvils were visited by 54 other bird species (mainly smaller species) that collected the broken shell fragments. The frequency of visits to anvils differed among species and changed over the course of the breeding season, but anvils were especially used by females during the pre-laying period. Our study is the first description of such widespread exploitation of thrush anvils by other bird species, and we think that this phenomenon has been overlooked owing to the difficulties in recording anvils located, for example, on single small stones, stumps of felled trees and man-made objects such as glass bottles. We conclude that thrush anvils can be an important source of calcium for many bird species that adapt behaviourally to use these places. Hence, anvils should be recognized as localized hotspots for bird diversity.

Egg concealment is an antipredatory strategy in a cavity‐nesting bird

AbstractBirds have developed different behavioural strategies to reduce the risk of predation during the breeding period. Bird species that nest in the open often cover their eggs to decrease the risk of predators detecting the clutches. However, in cavity nesters, the potential functions of egg covering have not been explored despite some bird species that nest in cavities also covering their eggs as open nesters do. We analysed whether egg covering is an antipredatory behaviour in the blue tit (Cyanistes caeruleus). We simulated an increase in the perceived risk of predation at experimental nests by adding predator scent inside the nest boxes during the egg‐laying period, whilst adding lemon essence or water to control nest boxes. Birds exposed to predator chemical cues in the nest of experimental pairs more frequently covered their eggs than birds exposed to an odorous control. These results suggest that egg covering may have evolved as an antipredatory behaviour also in cavity nesters to reduce the risk of egg predation and thus increase reproductive success in birds.

Positive roadside edge effects on artificial nest survival in a lowland Atlantic Forest.

Road construction is considered to be one of the primary causes of forest fragmentation, and little is known about how roads affect bird reproductive success. The objective of this study was to assess the survival rate of artificial nests along an edge associated with a highway and in the interior of a tabuleiro forest. The study was performed at the Sooretama Biological Reserve, on the margins of federal highway BR‐101, between September and October 2015. A total of 168 artificial nests with a Common quail (Coturnix coturnix) egg in each nest were placed along six sampling transects, at distances of 2, 25, 50, 100, 200, 400, and 800 m from the highway toward the forest interior. We used logistic regression and estimated daily survival rate (DSR) using the “Nest Survival” function in the program MARK to estimate artificial nest survival and assessed the effect of the distance from the highway. The artificial nest survival rate was significantly higher on the highway margins than at other distances. The results show that artificial nests located up to 25 m from the highway have a greater success probability (over 95%) and a significant decrease in success probability more than 50 m from the highway. Although we cannot rule out other nonroad‐specific edge effects on artificial nest predation, our results suggest that the impacts of the highway (e.g., noise, vibration, visual stimuli) cause predators to avoid the road's surroundings (up to 25 m into the forest) when selecting their feeding sites, which partially supports the predation release hypothesis.