Effect of supplementary food on age ratios of European turtle doves (Streptopelia turtur L.)

Efecto de la alimentación complementaria en la razón de edad de la tórtola europea (Streptopelia turtur L.) Son numerosas las aves de los hábitats agrícolas que tienen dificultades para encontrar suficiente alimento en los ecosistemas agrícolas intensivos y que, en los hábitats explotados de forma más extensiva, suelen ser atraídas por las fuentes antrópicas de alimento. La tórtola europea, Streptopelia turtur, se alimenta de semillas que se hallan en el suelo y es atraída inmediatamente por los cereales que se aportan como complemento a los comederos. El aporte complementario de alimento es una práctica habitual en la gestión de los cotos de caza de todo el mundo. Este estudio se realizó en 40 cotos de caza ubicados en el centro y el oeste de España: 20 zonas en las que se aportó alimentación complementaria para atraer a las tórtolas y 20 zonas de control sin comederos. En las zonas con alimentación complementaria, las razones de edad en el campo y en las aves cazadas fueron, respectivamente, un 20% y un 33% más elevadas que en las zonas de control, lo que indica que la alimentación complementaria tiene un efecto positivo en el éxito reproductivo en torno a las zonas con aporte de alimento complementario. Tanto la cantidad de alimento suministrado por día como el período en el que se aportó (20-120 días) se correlacionaron positivamente con la razón de edad en el campo y, con menos intensidad, con la razón de edad en las aves cazadas. Estos datos sugieren que el suministro de alimento extra puede aumentar el éxito reproductivo de esta especie si la cantidad aportada es suficientemente abundante y si se empieza a proporcionar a principios de la temporada de cría. No obstante, la presión cinegética también fue mayor en las zonas con aporte de alimento complementario, por lo que sería necesario analizar minuciosamente los efectos positivos y negativos de dicho aporte con vistas a determinar qué prácticas de gestión garantizarán la viabilidad de estas importantes poblaciones de tórtola europea.Many farmland birds have difficulties finding sufficient food in intensely managed agricultural ecosystems, and in more extensively worked landscapes they are often attracted to human–induced dietary sources. European turtle doves Streptopelia turtur feed on seeds collected on the ground, and are readily attracted to supplementary provided grain at feeding stations. Supplementary feeding is a common management practice on hunting estates around the world. This study was conducted in 40 hunting estates located in central west Spain: 20 sites where supplementary food was provided to attract turtle doves and 20 control sites without feeding stations. At sites with supplemental feeding, the field age ratio was 20% higher and the hunted age ratio was 33% higher than at control sites, indicating a positive effect of the food supplementation of the breeding success around supplemented sites. Both the amount of food provided per day and the amount of time where supplemental food was given (20–120 days) were positively correlated with the field age ratio and, less strongly, with the hunted age ratio. These data suggest that providing extra food can increase the breeding success of this species when the amount provided is sufficiently large and when supplementary food is provided early in the breeding season. However, hunting pressure was also higher at supplemented sites. Future studies should therefore closely monitor the positive and negative effects in order to ascertain which management practices will ensure the viability of these important European turtle dove populations.Efecto de la alimentación complementaria en la razón de edad de la tórtola europea (Streptopelia turtur L.) Son numerosas las aves de los hábitats agrícolas que tienen dificultades para encontrar suficiente alimento en los ecosistemas agrícolas intensivos y que, en los hábitats explotados de forma más extensiva, suelen ser atraídas por las fuentes antrópicas de alimento. La tórtola europea, Streptopelia turtur, se alimenta de semillas que se hallan en el suelo y es atraída inmediatamente por los cereales que se aportan como complemento a los comederos. El aporte complementario de alimento es una práctica habitual en la gestión de los cotos de caza de todo el mundo. Este estudio se realizó en 40 cotos de caza ubicados en el centro y el oeste de España: 20 zonas en las que se aportó alimentación complementaria para atraer a las tórtolas y 20 zonas de control sin comederos. En las zonas con alimentación complementaria, las razones de edad en el campo y en las aves cazadas fueron, respectivamente, un 20% y un 33% más elevadas que en las zonas de control, lo que indica que la alimentación complementaria tiene un efecto positivo en el éxito reproductivo en torno a las zonas con aporte de alimento complementario. Tanto la cantidad de alimento suministrado por día como el período en el que se aportó (20-120 días) se correlacionaron positivamente con la razón de edad en el campo y, con menos intensidad, con la razón de edad en las aves cazadas. Estos datos sugieren que el suministro de alimento extra puede aumentar el éxito reproductivo de esta especie si la cantidad aportada es suficientemente abundante y si se empieza a proporcionar a principios de la temporada de cría. No obstante, la presión cinegética también fue mayor en las zonas con aporte de alimento complementario, por lo que sería necesario analizar minuciosamente los efectos positivos y negativos de dicho aporte con vistas a determinar qué prácticas de gestión garantizarán la viabilidad de estas importantes poblaciones de tórtola europea

A new algorithm for the identification of dives reveals the foraging ecology of a shallow-diving seabird using accelerometer data

The identification of feeding events is crucial to our understanding of the foraging ecology of seabirds. Technology has made small devices, such as time-depth recorders (TDRs) and accelerometers available. However, TDRs might not be sensitive enough to identify shallow dives, whereas accelerometers might reveal more subtle behaviours at a smaller temporal scale. Due to the limitations of TDRs, the foraging ecology of many shallow-diving seabirds has been poorly investigated to date. We thus developed an algorithm to identify dive events in a shallowdiving seabird species, the Scopoli’s shearwater, using only accelerometer data. The accuracy in the identification of dives using either accelerometers or TDRs was compared. Furthermore, we tested if the foraging behaviour of shearwaters changed during different phases of reproduction and with foraging trip type. Data were collected in Linosa Island (35°51′33″N; 12°51′34″E) from 12 June to 8 September 2015 by deploying accelerometer data loggers on 60 Scopoli’s shearwaters. Four birds were also equipped with TDRs. TDRs recorded only 17.7% of the dives detected by the accelerometers using the algorithm. A total of 82.3% of dives identified by algorithm were too short or shallow to be detected by TDRs. Therefore, TDRs were not accurate enough to detect most of the dives in Scopoli’s shearwaters, which foraged mostly close to the sea surface. Our data showed that birds performed shorter foraging trips and dived more frequently in the early chick-rearing period compared with the late chick-rearing and incubation phases. Furthermore, parents dived more frequently during short foraging trips. Our results suggest that Scopoli’s shearwaters maximised their foraging effort (e.g. number of dives, short trips) during shorter foraging trips and during early chick-rearing

Are acoustical parameters of begging call elements of thin-billed prions related to chick condition?

Chicks of burrowing petrels use begging calls to advertise their hunger levels when parents arrived at the nest. In a previous study, adult thin-billed prions Pachyptila belcheri responded to higher begging call rates of their single chick by regurgitating larger meals. We tested whether acoustic parameters of begging call elements may also be involved in signalling. To describe variation in begging, we determined begging session parameters, namely the duration, number of calls and the mean and maximum rate of calling. We then digitised calls and carried out a semi-automatic extraction of six acoustic parameters of call elements, including mean and maximum acoustic frequency, the length of call elements and the location of the maximum frequency and amplitude within calls. Chicks showed strong individual differences in all parameters. While the session parameters were correlated with body condition and with the meal size the chick received, none of the acoustic parameters were related to body condition and provisioning. A cross-fostering experiment showed the same pattern, as only session parameters changed related to an experimentally altered body condition, while acoustical cues appear to play no role in signalling hunger levels. We suggest that this may be explained by the absence of sibling competition in these birds. As parents do not need to decide which chick to feed, immediate information on condition at the time of adult arrival may not be required

Variation in plasma oxidative status and testosterone level in relation to egg-eviction effort and age of brood-parasitic common cuckoo nestlings

To avoid competition for parental care, brood-parasitic Common Cuckoo (Cuculus canorus) nestlings evict all of the host's eggs and nestlings within a few days after hatching. Little is known about the physiological effects of eviction behavior on the cuckoo nestling's oxidative balance or about age-related variation in plasma oxidative status and testosterone level of developing birds. We examined whether the cuckoo nestling's plasma oxidative status was related to prior effort in eviction and quantified variation in the level of reactive oxygen metabolites, of nonenzymatic antioxidant capacity, and of testosterone concentration in plasma at various phases of the cuckoo's development. Levels of both reactive oxygen metabolites and antioxidant capacity were greater in older than in younger nestlings, suggesting that younger nestlings effectively counterbalance their increased production of free radicals, whereas, near fledging, levels of reactive oxygen metabolites increase despite improved antioxidant capacity. Possibly, overall energy expenditure increases with age and elevates the production of reactive oxygen species to a rate higher than what the antioxidant system could eliminate. Plasma testosterone level was the highest at nestlings' intermediate phase of growth. High levels of testosterone may be required during the period of fastest growth, and when the growth rate levels off near fledging, testosterone levels may also decline. Cuckoo chicks that evicted more host eggs from steeper nests had higher plasma levels of reactive oxygen metabolites shortly after the eviction period, suggesting that eviction is costly in terms of an increased level of oxidative stress. Para evitar la competencia por el cuidado parental, los polluelos parásitos de nidada de Cuculus canorus desalojan todos los huevos y los polluelos del hospedador a los pocos días después de la eclosión. Se sabe poco sobre los efectos fisiológicos del comportamiento de desalojo en el balance oxidativo de los polluelos de C. canorus o sobre la variación en el estatus oxidativo del plasma y el nivel de testosterona relacionado con la edad de las aves en desarrollo. Examinamos si el estatus oxidativo del plasma de los polluelos de C. canorus se relacionaba con un esfuerzo previo de desalojo y cuantificamos la variación en el nivel de metabolitos reactivos de oxígeno, la capacidad antioxidante no enzimática y la concentración de testosterona en el plasma en varias fases del desarrollo de C. canorus. Tanto los niveles de metabolitos reactivos de oxígeno como la capacidad antioxidante fueron superiores en los polluelos de mayor edad que en los más jóvenes, lo que sugiere que los polluelos de menor edad contrarrestan eficazmente el aumento de la producción de radicales libres, mientras que, cuando se apróximan al abandono del nido, los niveles de metabolitos reactivos de oxígeno aumentan a pesar de una mejora en la capacidad antioxidante. Posiblemente, el gasto total de energía se incrementa con la edad, elevándose la producción de formas reactivas de oxígeno a una tasa mayor de la que el sistema antioxidante puede eliminar. El nivel de testosterona en el plasma fue máximo en la fase intermedia del crecimiento de los polluelos. Pueden requerirse altos niveles de testosterona durante el período de mayor crecimiento y, cuando la tasa de crecimiento se estabiliza cerca del abandono del nido, los niveles de testosterona también podrián disminuir. Los polluelos de C. canorus que desalojaron más huevos del hospedador en nidos con una estructura más empinada tuvieron niveles de plasma de metabolitos reactivos de oxígeno en plasma más altos poco después del período de desalojo, sugiriendo que el desalojo es costoso en términos de un incremento en el nivel de estrés oxidativo

High prevalence of Trichomonas gallinae in wild columbids across western and southern Europe

Avian trichomonosis is known as a widespread disease in columbids and passerines, and recent findings have highlighted the pathogenic character of some lineages found in wild birds. Trichomonosis can affect wild bird populations including endangered species, as has been shown for Mauritian pink pigeons Nesoenas mayeri in Mauritius and suggested for European turtle doves Streptopelia turtur in the UK. However, the disease trichomonosis is caused only by pathogenic lineages of the parasite Trichomonas gallinae. Therefore, understanding the prevalence and distribution of both potentially pathogenic and non-pathogenic T. gallinae lineages in turtle doves and other columbids across Europe is relevant to estimate the potential impact of the disease on a continental scale

Hemosporidian blood parasites in seabirds—a comparative genetic study of species from Antarctic to tropical habitats

Whereas some bird species are heavily affected by blood parasites in the wild, others reportedly are not. Seabirds, in particular, are often free from blood parasites, even in the presence of potential vectors. By means of polymerase chain reaction, we amplified a DNA fragment from the cytochrome b gene to detect parasites of the genera Plasmodium, Leucocytozoon, and Haemoproteus in 14 seabird species, ranging from Antarctica to the tropical Indian Ocean. We did not detect parasites in 11 of these species, including one Antarctic, four subantarctic, two temperate, and four tropical species. On the other hand, two subantarctic species, thin-billed prions Pachyptila belcheri and dolphin gulls Larus scoresbii, were found infected. One of 28 thin-billed prions had a Plasmodium infection whose DNA sequence was identical to lineage P22 of Plasmodium relictum, and one of 20 dolphin gulls was infected with a Haemoproteus lineage which appears phylogenetically clustered with parasites species isolated from passeriform birds such as Haemoproteus lanii, Haemoproteus magnus, Haemoproteus fringillae, Haemoproteus sylvae, Haemoproteus payevskyi, and Haemoproteus belopolskyi. In addition, we found a high parasite prevalence in a single tropical species, the Christmas Island frigatebird Fregata andrewsi, where 56% of sampled adults were infected with Haemoproteus. The latter formed a monophyletic group that includes a Haemoproteus line from Eastern Asian black-tailed gulls Larus crassirostris. Our results are in agreement with those showing that (a) seabirds are poor in hemosporidians and (b) latitude could be a determining factor to predict the presence of hemosporidians in birds. However, further studies should explore the relative importance of extrinsic and intrinsic factors on parasite prevalence, in particular using phylogenetically controlled comparative analyses, systematic sampling and screening of vectors, and within-species comparisons

Long-term species, sexual and individual variations in foraging strategies of fur seals revealed by stable isotopes in whiskers

Background: Individual variations in the use of the species niche are an important component of diversity in trophic interactions. A challenge in testing consistency of individual foraging strategy is the repeated collection of information on the same individuals. Methodology/Principal Findings: The foraging strategies of sympatric fur seals (Arctocephalus gazella and A. tropicalis) were examined using the stable isotope signature of serially sampled whiskers. Most whiskers exhibited synchronous delta C-13 and delta N-15 oscillations that correspond to the seal annual movements over the long term (up to 8 years). delta C-13 and delta N-15 values were spread over large ranges, with differences between species, sexes and individuals. The main segregating mechanism operates at the spatial scale. Most seals favored foraging in subantarctic waters (where the Crozet Islands are located) where they fed on myctophids. However, A. gazella dispersed in the Antarctic Zone and A. tropicalis more in the subtropics. Gender differences in annual time budget shape the seal movements. Males that do not perform any parental care exhibited large isotopic oscillations reflecting broad annual migrations, while isotopic values of females confined to a limited foraging range during lactation exhibited smaller changes. Limited inter-individual isotopic variations occurred in female seals and in male A. tropicalis. In contrast, male A. gazella showed large inter-individual variations, with some males migrating repeatedly to high-Antarctic waters where they fed on krill, thus meaning that individual specialization occurred over years. Conclusions/Significance: Whisker isotopic signature yields unique long-term information on individual behaviour that integrates the spatial, trophic and temporal dimensions of the ecological niche. The method allows depicting the entire realized niche of the species, including some of its less well-known components such as age-, sex-, individual- and migration-related changes. It highlights intrapopulation heterogeneity in foraging strategies that could have important implications for likely demographic responses to environmental variability

Plasticity versus repeatability in seabird migratory behaviour

Pelagic seabird populations can use several discrete wintering areas, but it is unknown if individuals use the same wintering area year after year. This would have consequences for their population genetic structure and conservation. We here study the faithfulness of individuals to a moulting area within and among years in a small pelagic seabird, the Thin-billed prion, which moult their primary feathers during the early part of the non-breeding period. According to stable carbon isotope ratios (δ13C) of these feathers, 90% of Thin-billed prions moult in Antarctic and 10% in South American waters. Repeated samples from individuals in 2 or 3 years indicated that several birds changed between Antarctic and South American moulting areas or vice versa. However, individuals moulting in an area in one year were more likely to do so again. Four out of five adults maintained highly conserved δ13C over the extended moulting period. One bird, however, had systematic changes in δ13C indicating latitudinal movements between the two areas during moult. Thus, the present data show that this seabird species has a highly flexible migratory strategy, not only at the population level, but also at the individual level, enabling these seabirds to exploit a highly unpredictable environment

Can the intake of antiparasitic secondary metabolites explain the low prevalence of hemoparasites among wild Psittaciformes?

Background: Parasites can exert selection pressure on their hosts through effects on survival, on reproductive success, on sexually selected ornament, with important ecological and evolutionary consequences, such as changes in population viability. Consequently, hemoparasites have become the focus of recent avian studies. Infection varies significantly among taxa. Various factors might explain the differences in infection among taxa, including habitat, climate, host density, the presence of vectors, life history and immune defence. Feeding behaviour can also be relevant both through increased exposure to vectors and consumption of secondary metabolites with preventative or therapeutic effects that can reduce parasite load. However, the latter has been little investigated. Psittaciformes (parrots and cockatoos) are a good model to investigate these topics, as they are known to use biological control against ectoparasites and to feed on toxic food. We investigated the presence of avian malaria parasites (Plasmodium), intracellular haemosporidians (Haemoproteus, Leucocytozoon), unicellular flagellate protozoans (Trypanosoma) and microfilariae in 19 Psittaciformes species from a range of habitats in the Indo-Malayan, Australasian and Neotropical regions. We gathered additional data on hemoparasites in wild Psittaciformes from the literature. We considered factors that may control the presence of hemoparasites in the Psittaciformes, compiling information on diet, habitat, and climate. Furthermore, we investigated the role of diet in providing antiparasitic secondary metabolites that could be used as self-medication to reduce parasite load. Results: We found hemoparasites in only two of 19 species sampled. Among them, all species that consume at least one food item known for its secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, were free from hemoparasites. In contrast, the infected parrots do not consume food items with antimalarial or even general antiparasitic properties. We found that the two infected species in this study consumed omnivorous diets. When we combined our data with data from studies previously investigating blood parasites in wild parrots, the positive relationship between omnivorous diets and hemoparasite infestation was confirmed. Individuals from open habitats were less infected than those from forests. Conclusions: The consumption of food items known for their secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, as well as the higher proportion of infected species among omnivorous parrots, could explain the low prevalence of hemoparasites reported in many vertebrates