Response Of Birds Research Articles

Landscape context mediates the physiological stress response of birds to farmland diversification

Abstract Farmland diversification practices are increasingly adopted to help reverse biodiversity declines in agroecosystems. However, evidence for the effectiveness of this approach often comes from documenting the species attracted to particular farming systems or landscapes, rather than their underlying physiological states that ultimately determine population growth or decline over the longer term. Across 38 organic, mixed‐produce farms spanning the US west coast, we quantified three physiological biomarkers that are widely used to capture variation in short‐ and long‐term stress responses for nine bird species with diverse life‐history traits. While controlling for other potentially confounding variables, we used multilevel models to examine the association between bird physiological conditions, landscape context and local farm management practices, including the integration of livestock, and cropland composition and configuration. Birds generally had lower stress responses on more‐locally diverse farms and in landscapes with higher amounts of semi‐natural cover. However, interactions between farm diversity and landscape context suggested birds were less stressed on more diverse farms in simpler landscapes, but more stressed and in poorer condition on more diverse farms embedded within complex landscapes. We found no differences in stress responses among birds in relation to their degree of human association (synanthropy), which suggests generality in our findings. Synthesis and applications. Birds were often less stressed on more diverse farms. However, these patterns were mediated by landscape context: birds were less stressed on more diverse farms in simplified landscapes, but more stressed on more diverse farms within complex landscapes. This means land managers might not see uniform effects of local diversification schemes across different landscape contexts. Our results underscore the need to consider responses related to physiological health status, in addition to species richness and abundance, to determine the effectiveness of farm management for biodiversity conservation.

Effect of acute exposure to high ambient temperature on the thermal, metabolic and hygric physiology of a small desert bird

The intensity and frequency of extreme weather events, such as heat waves, are increasing as a consequence of global warming. Acute periods of extreme heat can be more problematic for wildlife than a chronic increase in mean temperature, to which animals can potentially acclimatise. Predicting effects of heat exposure requires a clear understanding of the capacity of individuals to respond to heat waves, so we examined the physiological response of a small desert bird, the zebra finch (Taeniopygia guttata), after acute previous exposure to high ambient temperature, simulating heatwave-like conditions. The standard physiology of the zebra finches was unaffected by prior exposure to heatwave-type conditions, suggesting that periodic exposure to heatwaves is unlikely to impact their longer-term day-to-day energy and water requirements. When finches were thermally challenged, prior experience of heatwave-like conditions did not impact overall body temperature and evaporative water loss, but birds previously experiencing high temperatures did reduce their metabolic heat production, and the variance in water loss and metabolism between individuals was significantly lower. This suggests that some individuals are more likely to become dehydrated if they have not had prior experience of high temperatures, and do not prioritise water conservation over thermoregulation. However, our observations overall suggest that acute periods of heat exposure do little to modify the general physiology of small birds, supporting the hypothesis that periodic extreme heat events may be more problematic for them than chronic warming.

Transcriptome analysis indicates a broad range of toxic effects of Deepwater Horizon oil on Seaside Sparrows

In marine species, the transcriptomic response to Deepwater Horizon (DWH) oil implicated many biochemical pathways, with corresponding adverse outcomes on organ development and physiological performance. Terrestrial organisms differ in their mechanisms of exposure to polycyclic aromatic hydrocarbons (PAHs) and their physiological challenges, and may reveal either distinct effects of oil on biochemical pathways or the generality of the responses to oil shown in marine species. Using a cross-species hybridization microarray approach, we investigated the transcriptomic response in the liver of Seaside Sparrows (Ammospiza maritima) exposed to DWH oil compared with birds from a control site. Our analysis identified 295 genes differentially expressed between birds exposed to oil and controls. Gene ontology (GO) and canonical pathway analysis suggested that the identified genes were involved in a coordinated response that promoted hepatocellular proliferation and liver regeneration while inhibiting apoptosis, necrosis, and liver steatosis. Exposure to oil also altered the expression of genes regulating energy homeostasis, including carbohydrate metabolism and gluconeogenesis, and the biosynthesis, transport and metabolism of lipids. These results provide a molecular mechanism for the long-standing observation of hepatic hypertrophy and altered lipid biosynthesis and transport in birds exposed to crude oil. Several of the activated pathways and pathological outcomes shown here overlap with the ones altered in fish species upon exposure to oil. Overall, our study shows that the path of oil contamination from the marine system into salt marshes can lead to similar responses in terrestrial birds to those described in marine organisms, suggesting similar adverse outcomes and shared machinery for detoxification.

Multi-scale response of wetland bird assemblages to landscape patterns on a Neotropical island: when wetland type matters more than size

Understanding wetland bird responses to landscape patterns is central for wetland management and bird conservation. This is particularly relevant on islands, where most of the global extinctions have occurred. In this study, we identified landscape patterns in wetlands on Cozumel Island that best explained abundance of birds grouped in 13 trophic guilds at 3 spatial scales (145, 300, and 850 m radius from count points). By using ordination techniques and generalized linear models we found a scale dependent dissimilarity between the use of extensive estuarine and small inland brackish wetlands. At finer spatial scales, abundance of birds in trophic guilds that mainly use estuarine or inland brackish wetlands was associated with the proportion of land cover types of the corresponding wetland type, whereas at the broadest spatial scale, connectivity of such land cover types was more important. Abundance of birds in trophic guilds that do not prefer any particular type of wetland did not show any relationship with landscape diversity nor connectivity of land cover types, but their abundance showed relationships with specific land cover types from both estuarine and inland brackish wetlands as well as with bordering wetland vegetation. We concluded that the presence of continuous extents of land cover types of both extensive estuarine and small inland brackish wetlands are important for the conservation of distinct wetland bird assemblages on Cozumel Island.

Noise level and water distance drive resident and migratory bird species richness within a Neotropical megacity

A large body of evidence indicates that urbanization profoundly affects ecological communities, but the extent to which patterns are generalizable across regions, such as in the Neotropics, remains unclear. We examined responses of migratory and resident birds to human disturbance and habitat attributes in São Paulo, Brazil, a tropical megacity in South America. In 2017–2018, we surveyed birds across 31 landscapes distributed across the urban landscape and evaluated competing models that included five non-correlated variables explaining variation in species richness: ambient noise level, distance to water, tree cover, human population size, and impervious surface. We recorded 142 bird species, 128 of which were resident and 14 migratory. Richness of both resident and migratory birds declined with increasing noise level and distance to water, which best explained variation in bird communities among the sampled landscapes. Although resident and migratory birds presented similar response patterns to local and landscape attributes, noise level was the best predictor of migratory species occurrence, whereas distance to water best explained the occurrence of resident species. Our results suggest that, although tree cover is important to biodiversity in urbanized landscapes, proper management of urban water bodies and reduction of noise levels are also essential to maintaining avian diversity within tropical urban areas and suggest novel avenues for future research in tropical urban ecology.

Simulation-based reconstruction of global bird migration over the past 50,000 years

Migration is a widespread response of birds to seasonally varying climates. As seasonality is particularly pronounced during interglacial periods, this raises the question of the significance of bird migration during past periods with different patterns of seasonality. Here, we apply a mechanistic model to climate reconstructions to simulate the past 50,000 years of bird migration worldwide, a period encompassing the transition between the last glacial period and the current interglacial. Our results indicate that bird migration was also a prevalent phenomenon during the last ice age, almost as much as today, suggesting that it has been continually important throughout the glacial cycles of recent Earth history. We find however regional variations, with increasing migratory activity in the Americas, which is not mirrored in the Old World. These results highlight the strong flexibility of the global bird migration system and offer a baseline in the context of on-going anthropogenic climate change.

Food access modifies GnIH, but not CRH, cell number in the hypothalamus in a female songbird

Food deprivation or restriction causes animals to mount a stereotypical behavioral and physiological response that involves overall increases in activity, elevated glucocorticoid production, and (often) inhibition of the reproductive system. Although there is increasing evidence that these responses can differ in their degree or covariation between the sexes, most studies to-date on food restriction/deprivation have focused on male songbirds. We therefore aimed to characterize the behavioral, physiological, and neuroendocrine response to acute food deprivation in a female songbird using a nomadic species, the zebra finch. We quantified behavior during a 6.5 h food deprivation and then measured physiological and neuroendocrine responses of female birds at the 6.5 h timepoint. Within 1 h of acute food deprivation, female zebra finches increased foraging behaviors, and after 6.5 h of food deprivation, females lost 5% of their body mass, on average. Change in body mass was positively associated with elevated corticosterone and (contrary to findings in male zebra finches) negatively related to the number of gonadotropin inhibitory hormone-immunoreactive cells in the hypothalamus. However, there was no effect of food deprivation on corticotropin releasing hormone-immunoreactive cells in the hypothalamus. There was also no relationship between corticotropin releasing hormone-immunoreactive cell number and circulating corticosterone. Our results are consistent with the hypothesis that neuroendocrine responses to food deprivation differ between male and female songbirds. Future studies should work to incorporate sex comparisons to evaluate sex-specific neuroendocrine responses to acute stress.

Dynamic response of bird strike on honeycomb-based sandwich panels of composite leading edge

In general, results from the birdstrike tests are employed so that they can be used to validate numerical models and promote the use of numerical tools in aircraft design and the certification process. In this research, firstly, via three existing experiments, the numerical models of birdstrikes are verified, and the simulated methods and parameters are chosen, such as the bird EOS’ selection. And then, the finite element model of the honeycomb sandwich structure of the leading edge is established. Through the different impact speed, we examine the energy absorption of honeycomb sandwich materials, as well as their failure. This paper also discusses how the strengthened beam may avoid the breakdown. Bird impact resistant design provides guidance for the future. The rules and experiences of some bird-strike scenarios are summarized in the end, leading to improved design efficiency and safety, while significantly reducing certification costs.

ARTIFICIAL NEURAL NETWORKS FOR PREDICTION OF PHYSIOLOGICAL AND PRODUCTIVE VARIABLES OF BROILERS

ABSTRACT Due to a number of factors involving the thermal environment of a broiler cutting installation and its interaction with the physiological and productive responses of birds, artificial intelligence has been shown to be an interesting methodology to assist in the decision-making process. For this reason, the main aim of this work was to develop an artificial neural network (ANN) to predict feed conversion (FC), water consumption (Cwater), and cloacal temperature (tclo) of broilers submitted to different air dry-bulb temperatures (24, 27, 30, and 33°C) and durations (1, 2, 3, and 4 days) of thermal stress in the second week of the production cycle. Relative humidity and wind speed were fixed at 60% and 0.2 ms−1, respectively. The experimental data were used for the development of an ANN with supervised training using the Levenberg-Marquardt backpropagation algorithm. The ANN consisted of three input layers one hidden, and three output with sigmoidal tangent transfer functions with values between −1 and 1. The developed ANN has adequate predictive capacity, with coefficients of determination (R2) for tclo, FC, and Cwater of 0.79, 0.87, and 0.97, respectively. In this way, the proposed ANN can be used as a support for decision-making to trigger poultry heating systems for broiler breeding.

Multiple fragmented habitat-patch use in an urban breeding passerine, the Short-toed Treecreeper.

Individual responses of wild birds to fragmented habitat have rarely been studied, despite large-scale habitat fragmentation and biodiversity loss resulting from widespread urbanisation. We investigated the spatial ecology of the Short-toed Treecreeper Certhia brachydactyla, a tiny, resident, woodland passerine that has recently colonised city parks at the northern extent of its range. High resolution spatiotemporal movements of this obligate tree-living species were determined using radio telemetry within the urbanized matrix of city parks in Copenhagen, Denmark. We identified regular edge crossing behaviour, novel in woodland birds. While low numbers of individuals precluded a comprehensive characterisation of home range for this population, we were able to describe a consistent behaviour which has consequences for our understanding of animal movement in urban ecosystems. We report that treecreepers move freely, and apparently do so regularly, between isolated habitat patches. This behaviour is a possible driver of the range expansion in this species and may contribute to rapid dispersal capabilities in certain avian species, including Short-toed Treecreepers, into northern Europe. Alternatively, these behaviours might be common and/or provide an adaptive advantage for birds utilising matrix habitats, for example within urban ecosystems.

The distribution and frequency of detection of woodland birds after selective logging of a small woodland remnant in an agricultural landscape in inland southern Australia

The majority of studies into the response of birds to logging in Australian forests has been done in forest-dominated landscapes or relatively large forest blocks, where the surrounding landscape can ameliorate impacts. This is the first study to examine the response of birds to logging of a small, relatively isolated woodland remnant in a landscape dominated by agriculture, with a focus on declining woodland birds. Approximately two thirds of a 120 ha cypress-eucalypt woodland remnant was selectively logged. Eighty bird species in total were recorded 2–3½ years after logging, including 18 recognised as declining woodland birds. Sixty-four species were recorded in the unlogged area and 72 in the logged area. Of the 31 species recorded sufficiently frequently for analysis, 19 showed no statistical difference in occurrence between logged and unlogged areas at the power of the study, nine were more prevalent in unlogged areas and three more prevalent in logged areas. Declining woodland birds comprised 22½% of overall species and 33% of those more prevalent in unlogged areas. Mapping of records enabled the response of a subset of species to be examined in greater detail. Four species illustrate the range of responses by declining woodland birds: Eastern Yellow Robin Eopsaltria australis was confined to unlogged areas, White-browed Babbler Pomatostomus superciliosus favoured unlogged areas, Varied Sittella Daphoenositta chrysoptera favoured proximity to unlogged areas and Red-capped Robin Petroica goodenovii was widely distributed in both logged and unlogged areas. The likelihood of recovery of local woodland bird populations is discussed in the context of limited landscape connectivity and the recent colonisation of the remnant by the hyper-aggressive Noisy Miner Manorina melanocephala. White-browed Babbler and Eastern Yellow Robin are considered to be at high risk of local extinction in the remnant.

Does dietary supplementation with phytases affect the thermoregulatory and behavioral responses of pullets in a tropical environment?

Dietary supplementation of two types of phytases (fungal and bacterial) with different dosages (300 and 900 FTUs) was evaluated in the thermoregulatory and behavioral responses of replacement pullets in a tropical environment. 288 Hy-Line White laying birds with a mean weight of 639.60±6.05g, clinically healthy, and eight weeks old were used in the study. Respiratory rate (RR, breaths. min-1), Cloacal temperature (CT, °C), Surface temperature with feathers (STWF, °C), and Surface temperature featherless (STF, °C) were measured in the morning and afternoon. Behavioral data were observed through the following activities: sitting, eating, drinking, exploring feathers (EF), non-aggressive pecking (NAP), and object pecking (OP) recorded every 10min from 6 a.m. to 5 p.m. Environmental variables were measured along with thermoregulatory and behavioral responses. There was an interaction for RR between phytase and period of the day (P<0.05). The lowest RR (morning) was observed in fungal phytase. STF and STWF were higher (P<0.05) in the afternoon. Birds supplemented with fungal phytase showed lower STWF (P<0.05). The variables that contributed to explain physiological and behavioral responses are shown in order of importance for (i) periods of day: morning (sitting, STWF, drinking, eating, and CT) and afternoon (STF, STWF, OP, drinking, eating, RR and sitting); (ii) phytases: fungal (STF, STWF, RR, sitting, eating and drinking); and bacterial (RR, STF, STWF, CT and sitting). Thermoregulatory and behavioral responses were similar between dosages, but different between types of phytases. Birds supplemented with fungal phytase used sensible heat dissipation mechanisms and exhibited thermal comfort behaviors. The 300 and 900 FTUs phytase doses did not influence the thermoregulatory and behavioral responses of birds, while they showed natural heat dissipation and heat stress behaviors in the afternoon. We recommend a dietary supplementation of 300 FTUs fungal phytases.

The Short-Term Response of Coastal Thicket Bird Communities to Fire in the Southeastern Cape, South Africa

Fire ecological research within the Cape Floristic Region is largely restricted to fynbos vegetation and, amongst fauna, birds. Nothing is known about post-fire responses of birds in subtropical thicket, which burns on much longer cycles than fynbos. Extensive fires in subtropical thicket along the southeastern Cape coast (in the Knysna area during June 2017) presented the opportunity to assess the response of these birds to fire. We predicted that (1) fire reduces bird species diversity, richness and abundance in thicket during the first two years post-fire; and (2) fire changes feeding guild composition and results in the loss of frugivorous birds. Bird surveys (point counts) were undertaken between 12- and 21-months post-fire in burnt (n =7) and unburnt (n = 7) thicket sites to determine bird community structure and abundance. A total of 66 bird species and 2404 individuals were recorded of which 52 species and 1176 individuals were recorded in burnt thicket and 60 species and 1228 individuals in unburnt thicket. Ten species occurred only in burnt thicket and 13 species only in unburnt thicket. There was a 21% loss of bird species (mainly forest birds) after fire. The Sorenson similarity coefficient was 60% for bird species composition between burnt and unburnt thicket. The most common feeding guilds in terms of richness and abundance in both burnt and unburnt thicket were insectivores and generalists. Frugivores were most abundant in unburnt thicket, whereas granivores were most abundant in burnt thicket. Changes in thicket bird community composition following the fire were minor and are likely to be short-lived as thicket shrubs re-sprout vigorously after fire resulting in rapid recovery of vegetation and thus bird habitat structure.

Traffic noise as a potential stressor to offspring of an urban bird, the European Starling

Anthropogenic disturbances induce stress in a variety of urban species. We examined the effects of traffic noise on the physiological stress response of nestling European Starlings (Sturnus vulgaris). Nest boxes were randomly assigned to either an experimental (increased urban noise played in nest box) or a control (typical urban/ambient noise) group. Heterophil/lymphocyte (H/L) ratios were determined to estimate physiological stress of nestlings at 11 and 15 days of age. Higher H/L ratios are associated with increased stress responses in birds. We predicted that nestlings in the experimental treatment would have higher H/L ratios and lower condition and fledging success than those in the control group on both days 11 and 15, but we detected no such differences on either day. Day 15 experimental nestlings, however, showed a non-significant trend toward lower H/L ratios than did day 15 control nestlings. We also examined whether nestlings became habituated (lower H/L ratios on day 15 than day 11) or sensitized (higher H/L ratios on day 15) to urban noise over time. There was a non-significant trend for experimental nestlings to have lower H/L ratios on day 15 than day 11, but no such pattern was detected in control nestlings. Our findings suggest that constant traffic noise is not stressful to nestlings in this urban-thriving species.

Habitat amount versus connectivity: An empirical study of bird responses

Habitat loss is widely acknowledged as a key driver of global biodiversity decline. However, whether biodiversity loss occurs in response to reductions in habitat amount versus reductions in connectivity in fragmented landscapes is debated. A challenge in resolving this issue is that measures of the amount of native woody vegetation cover and those calculated for structural connectivity are often highly correlated. Using multi-season detection-occupancy models we address the question: After accounting for the effects of native woody vegetation cover, what is the contribution of structural connectivity to site occupancy, site persistence and site colonization by birds? In this context, structural connectivity corresponded to the configuration of vegetation cover in the landscape surrounding our sites. We constructed multi-season detection-occupancy models for 44 individual bird species based on long-term field surveys in the temperate woodlands of eastern Australia. We found responses to vegetation amount were far more prevalent than responses to structural connectivity (35 vs 6 species). The range of responses by different species to vegetation amount, to structural connectivity, or to both, suggests that these elements have different effects on the processes of occupancy, persistence and colonization. The predominance of vegetation amount effects in our study, particularly the positive effects for a range of species of conservation concern, suggests the critical importance of both conserving existing areas of native vegetation cover and increasing the amount of that cover. At least for birds, efforts to physically connect particular patches may have relatively less benefit compared to programs to boost overall vegetation cover.

Response of colonial Peruvian guano birds to flying UAVs: effects and feasibility for implementing new population monitoring methods.

BackgroundDrones are reliable tools for estimating colonial seabird numbers. Although most research has focused on methods of improving the accuracy of bird counts, few studies have evaluated the impacts of these methods on bird behavior. In this study, we examined the effects of the DJI Phantom 3 drone approach (altitude, horizontal and vertical descent speeds) on changes in the intensity of behavioral response of guano birds: guanay cormorants (Phalacrocorax bougainvilli), Peruvian boobies (Sula variegata) and Peruvian pelicans (Pelecanus thagus). The breeding and non-breeding condition was also evaluated.MethodsEleven locations along the Peruvian coast were visited in 2016–2017. Drone flight tests considered an altitude range from 5 to 80 m from the colony level, a horizontal speed range from 0.5 to 15 m/s, and a vertical descent speed range from 0.5 to 3 m/s. The intensity of the behavioral response of birds was scored and categorized as: 0-no reacting, 1-head pointing to the drone (HP), 2-wing flapping (WF), 3-walking/running (WR) and 4-taking-off/flying (TK). Drone noise at specific altitudes was recorded with a sound meter close to the colony to discriminate visual from auditory effects of the drone.ResultsIn 74% of all test flights (N = 507), guano birds did not react to the presence of the drone, whereas in the remaining flights, birds showed a sign of discomfort: HP (47.7%, N = 130), WF (18.5%), WR (16.9%) and TK (16.9%). For the drone approach tests, only flight altitude had a significant effect in the intensity of the behavioral response of guano birds (intensity behavioral response <2). No birds reacted at drone altitudes above 50 m from the colony. Birds, for all species either in breeding or non-breeding condition, reacted more often at altitudes of 5 and 10 m. Chick-rearing cormorants and pelicans were less sensitive than their non-breeding counterparts in the range of 5–30 m of drone altitude, but boobies reacted similarly irrespective of their condition. At 5 m above the colony, cormorants were more sensitive to the drone presence than the other two species. Horizontal and vertical flights at different speeds had negligible effects (intensity behavioral response <1). At 2 m above the ground, the noise of the cormorant colony was in average 71.34 ± 4.05 dB (N = 420). No significant differences were observed in the drone noise at different flight altitudes because the background noise of the colony was as loud as the drone.ConclusionsIt is feasible to use the drone DJI Phantom 3 for surveys on the guano islands of Peru. We recommend performing drone flights at altitudes greater than 50 m from guano bird colonies and to select take-off spots far from gulls. Likewise, this study provides a first step to develop guidelines and protocols of drone use for other potential activities on the Peruvian guano islands and headlands such as surveys of other seabirds and pinnipeds, filming and surveillance.

Melatonin mends adverse temporal effects of bright light at night partially independent of its effect on stress responses in captive birds

ABSTRACTEcological artificial light at night (ALAN) has been increasingly associated with negative effects on the behavior and ecology of wild birds. However, the impacts of short-term bright ALAN on the temporal biology of companion animals and the underlying mediating mechanism are unknown. We evaluated impacts of 1X60-min/middle night ALAN (200 lux, λDominant = 460 nm) nightly with or without melatonin administration on growth performance, reproductive capacity, food and water intake, and stress responses in Australian budgerigars (Melopsittacus undulatus) under captivity. 36 birds were housed in pairs under natural photoperiod and were equally divided into three groups: control, natural conditions; ALAN, control + ALAN; and melatonin, ALAN + melatonin in the drinking water during the dark period. Birds were regularly monitored for body mass, egg production, and hatchability over four months. Food intake, water consumption, and daily rhythm of fecal corticosterone were also evaluated. ALAN increased mass gain, food intake, water consumption, and drastically decreased reproductive capacity, whereas stress responses were markedly augmented. Melatonin restored food and water intake to control levels but partly reversed mass gain. Melatonin failed to ameliorate the impaired reproductive capacity despite reducing the stress responses to basal levels. These results suggest that the ALAN-induced negative impacts cannot be attributed solely to direct effects of melatonin suppression or/and exacerbated stress responses and the involvement of other photoperiodic pathway components warrant further studies. Finally, the results of our study may be of importance for improving the housing conditions of companion animals at least as concern bright ALAN exposures.

The impact of age and feeding length on phytase efficacy during the starter phase of broiler chickens

Phytase is of importance to the poultry industry because of its ability to hydrolyze phytate and release phosphorus (P) for use by poultry. However, the effect of age on phytase efficacy is not fully understood. A total of 864 day-old broiler chicks were used to investigate the effect of age and feeding length on phytase efficacy using growth performance, mineral utilization, and tibia ash as response criteria of evaluation. The experiment was arranged as a 3 × 2 × 2 factorial in a randomized complete block design with 3 diets including; a positive control (PC; 0.4% non-phytate P (nPP)), a negative control (NC; 0.2% nPP) and a NC diet supplemented with phytase at 2,000 FYT/kg; 2 ages (i.e., days 14 and 22); and 2 feeding lengths (i.e., 2 and 5 D) with 8 replicates each. Birds fed the NC had decreased (P < 0.01) body weight gain and feed efficiency compared with birds fed the PC regardless of age or feeding length. Similarly, birds fed the phytase-supplemented diet had improved (P < 0.01) performance as compared to birds fed the NC regardless of age. There were no significant differences in P utilization between birds fed for 2 to 14 D or 22 D and birds fed for 5 D to both ages. However, phytase was more efficacious at day 14 than day 22 when mineral utilization was considered because the super dose of phytase elicited greater response in birds fed the phytase supplemented diet for 2 D until day 14. In contrast, percentage tibia ash improved (P < 0.01) in birds fed phytase supplemented diet for 5 D at both ages as compared with birds fed for 2 D. In conclusion, testing phytase products, even at high doses, for 2 D during the second week in the life cycle of broiler chicks, can be recommended from the results of this study.

Conservación en la ciudad: ¿Cómo influye la estructura del hábitat sobre la abundancia de especies de aves en una metrópoli latinoamericana?

A paucity of ecological research in urban ecosystems in Latin America limits the management of urban areas for biodiversity conservation. In addition, the majority of previous ecological studies in cities have focused on parks, ignoring most part of urban ecosystems. To provide robust scientific evidence for the management of urban areas for bird conservation, we investigate the influence of habitat variables on the abundance of native and exotic bird species in Santiago, Chile. During the reproductive season of 2017-2018, we surveyed birds and habitat variables at 455 points distributed throughout the city. We fit generalized linear models to evaluate the influence of habitat variables on individual bird species abundance. In 905 bird counts, we recorded 35 bird species (31 native and 4 exotic). The abundance of native birds (Zenaida auriculata, Elaenia albiceps, Troglodytes aedon, Turdus falcklandii, Zonotrichia capensis and Molothrus bonariensis) increased with woody vegetation cover. Points with greater shrub cover in the microhabitat exhibited a greater abundance of T. falcklandii, Z. capensis and E. albiceps. In contrast to the response of native birds, the abundance of exotic species (Columba livia and Passer domesticus) decreased with vegetation cover. Our results demonstrate the importance of woody vegetation to conserve native bird species in Santiago. Management of habitat that (1) avoids the loss of woody vegetation and (2) aims to increase trees and shrubs in urban areas with low vegetation cover will promote a greater abundance of native birds.

Electromagnetic 0.1-100 kHz noise does not disrupt orientation in a night-migrating songbird implying a spin coherence lifetime of less than 10 µs.

According to the currently prevailing theory, the magnetic compass sense in night-migrating birds relies on a light-dependent radical-pair-based mechanism. It has been shown that radio waves at megahertz frequencies disrupt magnetic orientation in migratory birds, providing evidence for a quantum-mechanical origin of the magnetic compass. Still, many crucial properties, e.g. the lifetime of the proposed magnetically sensitive radical pair, remain unknown. The current study aims to estimate the spin coherence time of the radical pair, based on the behavioural responses of migratory birds to broadband electromagnetic fields covering the frequency band 0.1-100 kHz. A finding that the birds were unable to use their magnetic compass under these conditions would imply surprisingly long-lived (greater than 10 µs) spin coherence. However, we observed no effect of 0.1-100 kHz radiofrequency (RF) fields on the orientation of night-migratory Eurasian blackcaps (Sylvia atricapilla). This suggests that the lifetime of the spin coherence involved in magnetoreception is shorter than the period of the highest frequency RF fields used in this experiment (i.e. approx. 10 µs). This result, in combination with an earlier study showing that 20-450 kHz electromagnetic fields disrupt magnetic compass orientation, suggests that the spin coherence lifetime of the magnetically sensitive radical pair is in the range 2-10 µs.