Ecological markers to monitor migratory bird populations: Integrating citizen science and transboundary management for conservation purposes.

Countries share responsibility for the management and conservation of migratory bird species. However, a limited understanding of population dynamics hampers the implementation of harvest and transboundary management. Age-ratios and population density can be useful indicators to assess population dynamics to improve management and conservation actions. Here, the dynamics of an Atlantic population of Common quail Coturnix coturnix, using 32,508 quail samples and 4814 hunter questionnaires over a 20-year period (1996-2016) served as a comparative study for examining age-ratio patterns related to different geographic zones, population density and weather parameters. Results show that age-ratios varied over zones and years, specifically age-ratio 1 (AR1), used as an index of late breeding attempts, varied from 0.1 to 0.21. Age-ratio 2 (AR2), a surrogate of central recruitment, varied from 0.16 to 0.66. Finally, age-ratio 3 (AR3), used as an indicator of the population's annual breeding success, varied from 3.69 to 6.68. Age-ratio is linked to internal and external factors (i.e. effect of rainfall, variations over time and density-dependent relationships) depicting how quail age groups make segregated migration in time and space. Quail age groups perform a complex pattern of migration because of entwined changes in abundance, migration routes and timing, influencing population connectivity and dynamics. Our findings highlight the relevance of citizen science and transboundary agreements to improve management and conservation measures of migrant species. Administrations and policy-makers in developed and developing countries must coordinate efforts to engage hunters in a participatory management systems to achieve sustainability.

Time, geography and weather provide insights into the ecological strategy of a migrant species.

Farmland and migratory bird populations are in decline. The Common quail (Coturnix coturnix) provides an exception to this trend and its populations have remained stable over the last two decades. However, some basic facts regarding quail biology and ecology, such as the geographic distribution of age and sex classes during the summer, remain poorly understood. We analyzed 43,194 Spanish quail ringing records from 1961 to 2014 to assess the effects of geography and weather conditions on the probability that individuals will be ringed during the various stages of their annual cycle (arrival -spring migration-, stationary breeding period, departure -autumn migration- and winter) for the different quail age-sex classes over time. We found that spatial distribution of the age and sex classes can be explained by date, latitude, longitude, altitude, rainfall, and temperature. Our results suggest that date accounts for most of the variation in the distribution of quail age classes, followed by the weather variables, and then latitude, and altitude. Similarly, date also accounts for most of the variation in the distribution of the two sexes. These results could partially explain why this species has avoided population decline, since its ecological strategy is based on its temporal and spatial distribution combined with the segregation of age and sex groups. We hypothesize that the distribution of quail age and sex classes follows variations in weather and habitat suitability to exploit seasonal and geographic variations in resource availability. The migratory and nomadic movements of quail, combined with the occurrence of multiple breeding attempts within a single season, may also allow these birds to overcome the impacts of predators and anthropogenic environmental change. Conservation and management efforts should therefore take account of these age and sex related temporal and spatial patterns.

Body proportions for the facilitation of walking, running and flying: the case of partridges.

BACKGROUND: Predation is one of the most important natural selection forces. Prey species can optimize feeding behavior and escape from predators based on mobility conditioned by body proportions. With age, mobility capacity increases and individuals are more efficient in finding resources and safety (e.g., food and refuge). Birds' mobility is driven by the dimensions, of the head and torso, as well as the extremities and flight feathers. To assess the relationship between body traits and to understand how body proportions are organized in wild Red-legged partridges (Alectoris rufa), we used biometric data from nearly 14,000 individuals, obtained during a long-term study (1988-2011) on a wild population. RESULTS: We used GLMs and regressions to model the relationship between body mass and the size of body parts. We found that wing length was the morphological part best explained by other body trait measures. Wing length models were better predictors in juveniles than in adults and in females than in males. Wing length and feather length, mass and total length are the most strongly related parts; mass and wing length, total length and feather length are moderately related. The association between mass and wing length is intermediated by feather length and total length. CONCLUSIONS: Social inclusion, feeding and predator evasion may be affected by body structure intermediated by mobility and health. Our results suggest that proportions of the body, extremities and flight feathers drive mobility which is intimately associated with ecology, biological efficiency, health and physical optimization. Our findings showed that wing size was strongly allied to other body part measurements, enhancing the importance of body structure conformation for flight. Our study highlights the scaled relationship of body structure among age-sex classes and its relevance to social cohesion, flock movement and the balance between predation and starvation.

Reply to the comment on "Synchronizing biological cycles as key to survival under a scenario of global change: The Common quail (Coturnix coturnix) strategy" by Rodriguez-Teijeiro et al.

Two methodological criticisms of our paper "Synchronizing biological cycles as key to survival under a scenario of global change: The Common quail (Coturnix coturnix) strategy" (Nadal et al., 2018) were proposed in the comment by Rodriguez-Teijeiro et al. (2018) regarding: 1) our estimates of the mean date of arrival, duration of stay and departure stages in the different regions studied; and 2) the analyses carried out to correlate the phenology of the species with changes in the climate variables. The conceptual model that we presented relates the dynamics of this quail population, which moves between short periods of stays, and the spatio-temporal structure of their geographic distribution data, in order to understand the ecology of these birds and to link their movement and residency patterns with geographical area and climate conditions. The probability that quail are resident in a region on any particular date is a result of their overall ecological strategy. We believe that Rodríguez-Teijeiro et al. (2018) have misunderstood our model, leading to their criticism of the statistical tests that we applied.

The effects of scaling on age, sex and size relationships in Red-legged Partridges.

Wild birds differ in size according to their age and sex, adult birds being larger than juveniles. In the galliforms, males are larger than females, in contrast to some groups, such as the raptors, in which the females are larger. Size generally influences the rank hierarchy within a group of birds, although the age, sex, temperament and behaviour of an individual may override its size related rank order. The scaled size of birds according to age and sex affects their physiology and behaviour. Precise details of body-size differences by age and sex are poorly known in most partridge species. We measured 13,814 wild partridges in a homogenous population over 14 years of study to evaluate size differences within a uniform habitat and population management regime. We show that wild Red-legged Partridges have scaled mass, and body- and wing-lengths consistent with age/sex classes. Power functions between mass and body-length (as a proxy for walking efficiency), and between mass and wing-length (for flight efficiency) differ between juvenile females and males, and adult females and males. We discuss these findings and their physiological, behavioural and ecological implications.

Synchronizing biological cycles as key to survival under a scenario of global change: The Common quail (Coturnix coturnix) strategy.

Breeding grounds are key areas for sustaining Common quail (Coturnix coturnix) populations as this species is characterised by short life expectancy that requires high offspring production. Annually, breeding quails make up to three breeding attempts in different places. However, the impact of climate warming on quail phenology is unknown. Here, we use a long-term study (1961-2014) of quail-ringing in Spain and data on variation in rainfall and temperature over the past 86years to evaluate how quails have responded to climate change in recent years. Our aim was to understand how this species is adapting to new farming practices and climate change. Our results suggest that increases in temperature and decreases in precipitation modify quail phenology. In hot years, an advance in mean arrival dates and stay stages but a delay in departure dates was found. However, in rainy years a delay in the mean start of the stay stage occurred. In cloudy areas, our findings show that quails advance their stay periods in hot and dry years and delay them in cold and rainy years. Accordingly, quail movements and breeding attempts are eco-synchronized sequentially in cloudy regions. Our results suggest that quails attempt to overcome the negative impacts of climate change and agricultural intensification by searching for alternative high-quality habitats. This strategy could explain how quail populations maintain viable and sustainable populations despite being legally harvested with regulated hunting.

Age and Sex Ratios in a High-Density Wild Red-Legged Partridge Population.

The dynamics of a wild red-legged partridge population were examined over a 14-year period in Spain to identify patterns in age and sex ratios in relation to weather parameters, and to assess the importance of these parameters in population dynamics and management. The results gave age ratios of 1.07 (but 2.13 in July counts), juvenile sex ratios of 1.01 and adult sex ratios of 1.47. Overall, 12% more females were hatched and female juvenile mortality was 7.3% higher than in males. Sex differential mortality explains the 19.2% deficit in adult females, which are more heavily predated than males during the breeding period. Accordingly, age ratios are dependent on sex ratios and both are density dependent. Over time, ratios and density changes appear to be influenced by weather and management. When the habitat is well conserved, partridge population dynamics can be explained by a causal chain: weather operates on net primary production, thereby affecting partridge reproduction and predation and, as a result, age and sex ratios in the October population. A reduction in the impact of predation (i.e. the effects of ground predators on eggs, chicks and breeding females) is the key factor to improve the conservation of partridge populations and associated biological processes.