Energy Requirements for Growth in Relation to Sexual Size Dimorphism in Marsh Harrier Circus aeruginosus Nestlings

Food consumption was measured in six female and seven male hand-raised marsh harrier (Circus aeruginosus) nestlings. Females consumed on average 4,321 g and males consumed 3,571 g of food during the nestling stage from 0 to 36 d. Total consumption until 56 d was 6,960 g and 5,822 g for females and males, respectively. On the basis of Fisher’s sex ratio theory, this food intake ratio of 0.46 (intake male/[intake male + female]) would explain the observed male-biased fledging sex ratio of 55% males in marsh harrier broods. Growth, gross energy intake, and metabolizable energy intake were measured, along with metabolism of the nestlings, enabling us to determine energy allocation. The assimilation quotient (Q = 0.72) did not differ systematically between the sexes. Differences in metabolic rates between males and females at 15 and 30 d of age were fully attributable to the difference in body mass. Sexual size dimorphism in marsh harriers (female body mass around 60 d of age is 1.28 times greater than male mass) did not fully explain the difference in food intake between male and female nestlings: an analysis of energy requirements for growth and body mass in 16 avian species shows that energy intake was less than proportional to the average body mass at release. The data presented in this study are in agreement with Fisher’s theory of inverse proportionality between the sex-specific ratios of energy requirements for growth and of offspring numbers in the marsh harrier population.

Time budgets and body temperatures of American Golden-Plover chicks in relation to ambient temperature

We studied time budgets of precocial chicks of American Golden-Plovers (Pluvialis dominica) on the tundra near Churchill, Manitoba, Canada, to assess how time budgets are influenced by environmental and body temperatures. Foraging time per day increased with increasing ambient temperatures and levels of solar radiation, as well as with age. This increase was due to an increase in the length of foraging bouts (i.e., the period of time in between two brooding bouts). The length of brooding bouts averaged 12 min, independent of ambient conditions or age. Body temperatures were lower under colder environmental conditions and increased as the chicks grew older. Based on measurements of cooling rates of penned chicks, we determined that at the end of a foraging bout, body temperature never fell below 35.5degreesC, which is high for a precocial chick. We suggest that in Churchill, American Golden-Plover chicks are not limited in their foraging time by ambient conditions, and they can collect sufficient food in the short periods of foraging that are available to them to sustain normal growth. By minimizing foraging bout length in favor of parental brooding, chicks may increase their digestive efficiency as well as save energy that would otherwise be expended on thermoregulation and locomotion

Data from: Aeroecology meets aviation safety: early warning systems in Europe and the Middle East prevent collisions between birds and aircraft

The aerosphere is utilized by billions of birds, moving for different reasons and from short to great distances spanning tens of thousands of kilometres. The aerosphere, however, is also utilized by aviation which leads to increasing conflicts in and around airfields as well as en-route. Collisions between birds and aircraft cost billions of euros annually and, in some cases, result in the loss of human lives. Simultaneously, aviation has diverse negative impacts on wildlife. During avian migration, due to the sheer numbers of birds in the air, the risk of bird strikes becomes particularly acute for low-flying aircraft, especially during military training flights. Over the last few decades, air forces across Europe and the Middle East have been developing solutions that integrate ecological research and aviation policy to reduce mutual negative interactions between birds and aircraft. In this paper we (1) provide a brief overview of the systems currently used in military aviation to monitor bird migration movements in the aerosphere, (2) provide a brief overview of the impact of bird strikes on military low-level operations, and (3) estimate the effectiveness of migration monitoring systems in bird strike avoidance. We compare systems from the Netherlands, Belgium, Germany, Poland and Israel, which are all areas that Palearctic migrants cross twice a year in huge numbers. We show that the en-route bird strikes have decreased considerably in countries where avoidance systems have been implemented, and that consequently bird strikes are on average 45% less frequent in countries with implemented avoidance systems in place. We conclude by showing the roles of operational weather radar networks, forecast models and international and interdisciplinary collaboration to create safer skies for aviation and birds

Study area and position of the bird radar.

<p>Map of the north-western part of the Balgzand intertidal area in the Wadden Sea, the Netherlands, showing the position of the radar (blue dot) and the transects used by visual observers (red arrows into the direction of observation). Concentric circles around the radar position are separated by a range of 1 km.</p

Average probability of detection (POD) as a function of range.

<p>Each scatter point refers to a distinct distance class of one of the transects and its corresponding subset of visual observations from , drawn on the horizontal axis at its mean range. The modelled POD equals the mean GAM prediction for these observations. The observed POD equals the proportion of these observations that could be matched to a radar track directly. Lines indicate the upper and lower 1 confidence intervals.</p

Average probability of detection (POD) per species in the radar range 0–1500 m.

<p>POD values are shown for the 10 most frequently observed species, from top to bottom ordered by body mass: Great Cormorant, Common Eider, Common Shelduck, European Herring Gull, Eurasian Curlew, Eurasian Oystercatcher, Common Gull, Black-headed Gull, Sandwich Tern and Common Tern. The modelled POD equals the mean GAM prediction for all visual observations within this 0–1500 m range. The observed POD equals the proportion of these observations that could be matched to a radar track directly. Black dots indicate the average body mass per species.</p

Coefficients of the best GAM model for the probability of detection.

<p>Stars indicate significance of each term according to a Wald test against the null hypothesis that the term is zero (*** p<0.001, ** p<0.01, * p<0.05).</p

GAM models for the probability of detection compared by AIC.

<p>POD = probability of detection, d = distance, m = mass, surf = surface dry/wet, alt = altitude, spec = species. df gives the (estimated) degrees of freedom of the model. “:” indicates an interaction of all the variables and factors appearing in the term. The degrees of freedom for the mass smooth term was restricted to 5. Stars indicate the significance of a model comparison according to a Chi-squared test between each model and the best (first) model (under assumption of df),</p>***<p>p<0.001,</p>**<p>p<0.01,</p>*<p>p<0.05.</p