Do small precocial birds enter torpor to conserve energy during development?

Precocial birds hatch feathered and mobile, but when they become fully endothermic soon after hatching, their heat loss is high and they may become energy depleted. These chicks could benefit from using energy-conserving torpor, which is characterised by controlled reductions of metabolism and body temperature (Tb). We investigated at what age the precocial king quail Coturnix chinensis can defend a high Tb under a mild thermal challenge and whether they can express torpor soon after achieving endothermy to overcome energetic and thermal challenges. Measurements of surface temperature (Ts) using an infrared thermometer showed that king quail chicks are partially endothermic at 2-10 days, but can defend high Tb at a body mass of ∼13 g. Two chicks expressed shallow nocturnal torpor at 14 and 17 days for 4-5 h with a reduction of metabolism by >40% and another approached the torpor threshold. Although chicks were able to rewarm endogenously from the first torpor bout, metabolism and Ts decreased again by the end of the night, but they rewarmed passively when removed from the chamber. The total metabolic rate increased with body mass. All chicks measured showed a greater reduction of nocturnal metabolism than previously reported in quails. Our data show that shallow torpor can be expressed during the early postnatal phase of quails, when thermoregulatory efficiency is still developing, but heat loss is high. We suggest that torpor may be a common strategy for overcoming challenging conditions during development in small precocial and not only altricial birds.

Resting metabolic rate and erythrocyte morphology in early development of thermoregulation in the precocial grey partridge (Perdix perdix)

In the early stages of development of thermoregulation in grey partridge, a typical precocial species, I measured the resting metabolic rate (RMR) and body temperature (Tb) in the thermoneutral zone (TNZ) and the parallel changes in the size of erythrocytes and their cell nuclei. The strong positive correlation between the mass-independent (residuals versus body mass) values of Tb and RMR indicates a close relationship, between these physiological parameters in the first week of life of partridges. In the ontogeny of this species, the dimensions of erythrocytes correlated inversely with the mass-specific metabolic rate (expressed in mW g(-1)), claiming its status as an important and metabolically useful measure of development. The correlation coefficient of these two variables, at the level of individual development within a species, has been further enhanced in the inter-specific analysis at the level of the order Galliformes. The characteristics of changes in the erythrocyte size, in parallel with the dynamics of the resting level of heat production development, in the important period when the thermoregulation is assuming its form in precocial birds, supply new data pertaining to this strategy of avian development.

Short- and long-term population dynamical consequences of asymmetric climate change in black grouse

Temporal asymmetry in patterns of regional climate change may jeopardize the match between the proximate and ultimate cues of the timing of breeding. The consequences on short- and long-term population dynamics and trends as well as the underlying mechanisms are, however, often unknown. Using long-term data from Finland, we demonstrate that black grouse (Tetrao tetrix) have responded to spring warming by advancing both egg-laying and hatching. However, early summer (the time of hatching) has not advanced, and chicks have to face colder post-hatching conditions. Demonstrating that these conditions are critical to post-hatching survival, we show that chicks are increasingly suffering higher mortality because they hatch too early. Consequently, breeding success and population size has severely declined over the past four decades. Finally, we modelled the impact of this particular climate change scenario on population dynamics and show that the mismatch can further explain the observed collapse of cyclic fluctuations. Because the evolutionary response of grouse is lagging behind the novel selective pressures, seasonally asymmetric climate change is likely to constitute an important determinant of future short- and long-term changes in the dynamics of black grouse populations.

Growth rate and thermoregulation in reared king quails (Coturnix chinensis)

Growth rate was investigated in king quails between 1st and 60th day of life. Gompertz growth constants were 0.075 in males and 0.056 in females. Colonic temperature (Tb) was measured in quails divided into four age groups (1-3, 7-10, 16-19, and 44-59 days old) in ambient temperatures set separately for each group. Metabolic rate was measured only in 44-59-day-old birds. The mean value of the thermoneutral body temperature (Tb at TNZ) in the active phase in the youngest quails was 39.0 degrees C. In 44-59-day-old quails, the resting metabolic rate in the thermoneutral zone (RMR at TNZ) was on average 9.44 mW g(-1) (1.66 cm3 O2 g(-1)h(-1)), without sex-specific differences. No such differences were found in this age group neither in Tb at TNZ, nor in minimal thermal conductance (Cmin). However, differences were found in the rate of metabolic heat production below the thermoneutral zone, even when mass-independent units were used. The maximum metabolic rate (Mmax) in 2-month-old males was 34.08 mW g(-1) (5.98 cm3 O2 g(-1)h(-1)), while in females 29.73 mW g(-1) (5.21 cm3 O2 g(-1)h(-1)). Heat-stressed 44-59-day-old quails elevated their Tb to as much as an average 44.1 degrees C in Ta of about 45 degrees C. The obtained growth model and a gradual development of the body temperature regulation mechanism in king quails followed the known strategy of development, typical for precocial birds. The sexual size dimorphism in the studied quails did not result in differences in thermoregulation parameters between the sexes, except for the rate of metabolic rate below thermoneutral zone.

Energy metabolism and thermoregulation in hand-reared chukars (Alectoris chukar)

Metabolic rate and colonic temperature were measured in chukars between 1st and 108th day of life (divided into six age groups: 1-3-days old, 1, 2, 3, and 4-weeks old and 3.5-months old) in ambient temperatures set separately for each group and ranging from -12 to 41 degrees C. The Gompertz growth constant for growing chukars (0.042) was close to the value obtained in earlier study for the grey partridge. Similarly as in other species of Galliformes, newly hatched chukar chicks had lower T(b) at TNZ (39.5 degrees C) than that found in older birds (41.3 degrees C in 4-weeks old). The body temperatures taken at TNZ in 2-weeks old chicks and older fitted neatly within allometrically predicted limits of body temperatures for adult birds. The values of RMR at TNZ followed closely a biphasic pattern, with the second phase correlating strongly with the body mass. The value of metabolic scope (the level of metabolic efficiency) for the youngest group was high (3.2) and exceeded the values obtained in earlier studies for other gallinaceous species, including the grey partridge. The obtained values of minimum wet thermal conductance for growing chukar chicks exceeded the predicted values by approximately 40% but the slopes of both lines were very similar. In chukars, the key stage in the expression of fully developed thermoregulatory capacities comes immediately after the first week of life (maintaining somewhat constant body temperature, evident drop in the value of RMR at TNZ and minimal thermal conductance). The model of gradual development of thermoregulation which could be derived from the experiments on chukar chicks was characteristic for typical precocial birds.

Ontogeny of thermoregulatory mechanisms in king penguin chicks (Aptenodytes patagonicus)

The rapid maturation of thermoregulatory mechanisms may be of critical importance for optimising chick growth and survival and parental energy investment under harsh climatic conditions. The ontogeny of thermoregulatory mechanisms was studied in growing king penguin chicks from hatching to the full emancipation observed at 1 month of age in the sub-Antarctic area (Crozet Archipelago). Newly hatched chicks showed small, but significant regulatory thermogenesis (21% rise in heat production assessed by indirect calorimetry), but rapidly became hypothermic. Within a few days, both resting (+32%) and peak (+52%) metabolic rates increased. The first week of life was characterised by a two-fold rise in thermogenic capacity in the cold, while thermal insulation was not improved. During the second and third weeks of age, thermal insulation markedly rose (two-fold drop in thermal conductance) in relation to down growth, while resting heat production was slightly reduced (-13%). Shivering (assessed by electromyography) was visible right after hatching, although its efficiency was limited. Thermogenic efficiency of shivering increased five-fold with age during the first weeks of life, but there was no sign of non-shivering thermogenesis. We conclude that thermal emancipation of king penguin chicks may be primarily determined by improvement of thermal insulation after thermogenic processes have become sufficiently matured. Both insulative and metabolic adaptations are required for the rapid ontogeny of thermoregulation and thermal emancipation in growing king penguin chicks.

Impact of hand-rearing on morphology and physiology of the capercaillie (Tetrao urogallus)

Morphological and physiological disparities between 20 captive and 11 wild capercaillies were determined. Birds, their pectoral and leg muscles, hearts, livers and gizzards were weighed. The length of small intestines and caeca were measured. Haemoglobin, haematocrit, glucose, triglycerides, total protein, uric acid and thyroid hormones as well as the cytochrome c-oxidase activity of the pectoral muscle and heart were determined. The glycogen and protein contents of pectoral and leg muscles and liver were analysed. Chemical composition (water, fat, protein, ash) of muscles and liver was determined. Captive males had heavier pectoral muscles than wild ones. The result was opposite in females. Wild birds had heavier hearts, livers, and gizzards, and also longer small intestines and caeca than captive birds. The cytochrome c-oxidase activity of pectoral muscle and heart was higher in wild than in hand-reared birds. The chemical composition of livers of wild birds differed significantly from that of hand-reared capercaillies. Plasma uric acid and T(4) concentrations were higher in captive than in wild birds. The observed differences in digestive system and liver can result in diminished ability of captive birds to utilise natural food nutrients. Decreased cytochrome c-oxidase activity of hand-reared birds can affect their takeoff and flying capacity and increase their vulnerability to predation. These facts may contribute to the low survival of hand-reared birds after release.

Shivering thermogenesis in leg and breast muscles of galliform chicks and nestlings of the domestic pigeon

We studied the ontogeny of shivering thermogenesis in breast and leg muscles of precocial galliforms (domestic fowl, grey partridge, and Japanese quail) and the altricial domestic pigeon using electromyography (EMG) and indirect calorimetry. Galliforms were able to increase heat production by shivering in leg muscles at the youngest age studied (1-2 d). Pectorals contributed to heat production from days 7-10 onward, but in the partridge and especially in the fowl, shivering by the pectorals was weaker than in the quail. In the pigeon, shivering began in pectorals and legs at 2 and 4 d of age, respectively, and pectorals had clearly the predominant role in thermogenesis. Despite the early beginning of electrical signs of shivering, significant thermogenesis did not appear in the pigeon before the age of 6 d. All galliforms shivered in bursts, like pigeons aged 2-4 d. From the age of 6 d onward, continuous shivering became predominant in the pigeon. In pectorals of 2-6-d-old pigeons, shivering did not increase linearly during decreasing ambient temperature, as in other muscles and species, but started abruptly, at full intensity. Furthermore, in 2-4-d-old pigeons, cooling induced movement activity in legs. The median frequency of shivering EMGs varied (1) with maturation of the muscle, (2) with size of the adult bird, and (3) between altricials and precocials.