Haematocrit correlates with tail ornament size in three populations of the Barn Swallow (Hirundo rustica)

1. Handicap models of sexual selection propose that male ornaments are indicators of male quality and that honesty is enforced by the costs imposed by the exaggerated ornamental traits. In long-distance migratory birds that feed on the wing, the aerodynamic cost of exaggerated ornamental characters should be particularly high because the size of the ornaments deviates from the natural selection optimum. During migration, birds are expected to raise their oxygen consumption in relation to the energetic demands imposed by their morphology. An increase of haematocrit is an adaptive response to enhance oxygen uptake and efficiency of transfer to the muscular tissues during spells of intense muscular activity.
2. The change of haematocrit of Barn Swallows ( Hirundo rustica ) after their arrival to the breeding sites, and the relationships between haematocrit values recorded after migration and the size of ordinary and sexually selected morphological characters in three Barn Swallow populations were analysed.
3. Males had higher haematocrit values than females. Individual haematocrit values declined after arrival to the breeding sites. Haematocrit values of males were significantly and positively correlated with the size of their ornamental tail but not correlated with other characters, thus suggesting that well-ornamented males, in order to arrive early, have to raise their haematocrit above the level of short-tailed males.
4. Males and females of similar tail length did not differ in their haematocrit, thus suggesting that sexual dimorphism in haematocrit might be functionally related to dimorphism in tail length.
5. Our results are consistent with the handicap principle because long-tailed males experience lower mortality and larger seasonal reproductive success compared with short-tailed males.     

Alteration in haematocrit values and plasma protein fractions during the breeding cycle of female pigeons, Columba livia

Haematocrit measurements and plasma protein electrophoresis were carried out in female pigeons (Columba livia) during the breeding cycle. Non-laying birds showed higher (p < 0.001) haematocrit values than those involved in courtship and mating, nest-building, incubation and feeding and brooding. Significant differences in relative percentage of various plasma protein fractions were observed as a function of breeding. Haematocrit could be a useful index to the non-laying status of pigeons like that in chickens, Gallus domesticus.     

Effect of endurance flight on haematocrit in migrating birds

The effects of an endurance flight on the haematocrit, the percentage of packed red blood cells per blood volume, were examined within the framework of six possible factors explaining possible changes in the haematocrit. Two approaches were adopted: (1) the haematocrit was studied in four species of passerine birds which landed on an Italian island after having crossed the Mediterranean Sea on their spring migration in a non-stop flight; (2) the haematocrit was evaluated in six individual red knots after a flight of 1, 2, 4 and 10 h in a wind tunnel and the data thus obtained compared with data on resting birds with or without food. In the four passerine species, the haematocrit decreased from 51% in fat birds to 48% in lean birds. In lean birds, the haematocrit dropped from 48% in birds with well-developed breast muscles to 36% in birds with emaciated breast muscles. In the red knots, the haematocrit was dependent on body mass in flying and resting birds. The haematocrit decreased from about 51% pre-flight to about 49% within 1 h of flight and remained at this level for up to 10 h of flight. Taking the results from the passerines and the red knots together, it seems that the haematocrit drops by a few percentage points within 1 h after the onset of flight, decreases very slowly with decreasing body mass and decreases more steeply in very lean birds having entered stage III of fasting. This indicates that dehydration is not an underlying factor in decreased haematocrit because if this were the case we would expect an increase with endurance flight. We found no effect of the presence of blood parasites on haematocrit. With the onset of flight, haemodilution may be adaptive, because it reduces blood viscosity and, thereby, energy expenditure by the heart, or it may be a sign of water conservation as an insurance against the risk of dehydration during long non-stop flights. During endurance flight, a reduction in the haematocrit may be adaptive, in that oxygen delivery capacity is adjusted to the decreased oxygen needs as body mass decreases. A decreasing haematocrit would also allow birds to reduce heart beat frequency and/or heart size, because blood viscosity decreases disproportionally with decreasing haematocrit. However, when energy stores are about to come to an end and birds increase protein breakdown, the haematocrit decreases even further, and birds probably become anaemic due to a reduced erythropoiesis.     

Plasma insulin concentrations during infusions of potassium and sodium chloride solutions into conscious splenectomized sheep

Haematocrit values, plasma osmolality and the plasma concentrations of sodium, potassium, chloride and insulin were measured in carotid arterial blood before, during and after intravenous infusion of NaCl (0.5 mol 1-1) and KCl (0.5 mol 1-1) at 2 ml min-1 for 105 min into six conscious splenectomized sheep. Hypertonic NaCl infusion was associated with a fall in haematocrit of 1.30 +/- 0.10% (P less than 0.001) and no consistent change in plasma insulin concentration occurred during this infusion. Hypertonic KCl infusion caused the haematocrit to increase by 1.70 +/- 0.39% (P less than 0.001) and the plasma insulin concentration to increase by 60.0 +/- 16.3 mu U ml-1 (P less than 0.01). It was concluded that this increase in insulin concentration was caused by elevation of the plasma potassium concentration and was not due to coincident increases in plasma chloride concentration or osmolality. Shrinkage of the extracellular fluid volume during KCl infusion made no major contribution to the increase in insulin concentration which was probably the result of increased release from the pancreas.     

Effect of litter size on blood haematocrit and liveweight in Booroola Merino and Merino ewes during pregnancy and the post-partum period

Blood haematocrit and liveweight were determined throughout pregnancy and the post-partum period in 217 Booroola Merino and Merino ewes in order to relate these parameters to litter size at birth. In pregnant ewes, haematocrit declined from three until five months gestation, rose immediately after parturition then declined until two months post-partum. During the third to fifth month of gestation, haematocrit decreased in proportion to litter size. Nonpregnant ewes, measured at similar intervals, did not show the same pattern. Haematocrit of nonpregnant animals was higher than that of triplet-bearing ewes at three, four and five months gestation, but was only significantly different to single- and twin-bearing ewes at five months. The liveweight of pregnant ewes increased up to parturition and then declined until two months post-partum. The liveweight of nonpregnant ewes increased over the experimental period. It was concluded that the number of foetuses a ewe carried had significant effects on the decline in haematocrit during pregnancy. Haematocrit was not a precise indicator of litter size in sheep. Haematocrit, ewe liveweight and ovulation rate together in a multiple regression only accounted for 37% of the variation in litter size.     

Different Environmental Drivers of Highly Pathogenic Avian Influenza H5N1 Outbreaks in Poultry and Wild Birds

A large number of highly pathogenic avian influenza (HPAI) H5N1 outbreaks in poultry and wild birds have been reported in Europe since 2005. Distinct spatial patterns in poultry and wild birds suggest that different environmental drivers and potentially different spread mechanisms are operating. However, previous studies found no difference between these two outbreak types when only the effect of physical environmental factors was analysed. The influence of physical and anthropogenic environmental variables and interactions between the two has only been investigated for wild bird outbreaks. We therefore tested the effect of these environmental factors on HPAI H5N1 outbreaks in poultry, and the potential spread mechanism, and discussed how these differ from those observed in wild birds. Logistic regression analyses were used to quantify the relationship between HPAI H5N1 outbreaks in poultry and environmental factors. Poultry outbreaks increased with an increasing human population density combined with close proximity to lakes or wetlands, increased temperatures and reduced precipitation during the cold season. A risk map was generated based on the identified key factors. In wild birds, outbreaks were strongly associated with an increased Normalized Difference Vegetation Index (NDVI) and lower elevation, though they were similarly affected by climatic conditions as poultry outbreaks. This is the first study that analyses the differences in environmental drivers and spread mechanisms between poultry and wild bird outbreaks. Outbreaks in poultry mostly occurred in areas where the location of farms or trade areas overlapped with habitats for wild birds, whereas outbreaks in wild birds were mainly found in areas where food and shelters are available. The different environmental drivers suggest that different spread mechanisms might be involved: HPAI H5N1 spread to poultry via both poultry and wild birds, whereas contact with wild birds alone seems to drive the outbreaks in wild birds.     

Considerations of blood parameters of largemouth bass, Micropterus salmoides

To evaluate physiological stress resulting from environmental influences, a haematological study of a natural population of largemouth bass, Micropterus salmoides , was undertaken to establish a 'normal' blood profile. Several parameters including haemoglobin concentration, haematocrit, erythrocyte count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma protein concentration and glucose levels were investigated. Haematocrit, haemoglobin, and total plasma protein were positively correlated with fish length. Haemoglobin and haematocrit were positively correlated with fish age while mean corpuscular haemoglobin, concentration was negatively correlated with fish age. Both haemoglobin and haematocrit values were related to erythrocyte counts.     

Microfilarial infections associated with body mass loss of Village Weavers Ploceus cucullatus

Haemoparasitic infections in wild birds have been widely studied in order to understand parasite–host relation- ships, but our understanding of their impact on the host's fitness is still limited. In this study, we quantified the associations between microfilarial infections and body mass and between microfilarial infections and haemato- crit values in Village Weavers Ploceus cucullatus. We screened blood samples (thin smear and buffy coat) for the presence of haemoparasitic infections and measured haematocrit values. Fifty-seven percent of 91 individuals screened carried a microfilarial infection but, contrary to expectations, no other haemoparasitic infections were detected in the blood samples. We found a negative relationship between microfilarial infection status and body mass, but no relationship between infection status and haematocrit values. Our results suggest that microfilarial infections may be associated with body mass loss in wild birds.     

Energetic demands during brood rearing in the Wheatear Oenanthe oenanthe

Daily energy expenditure of Wheatears Oenanthe oenanthe during the brood rearing period was measured using the doubly-labelled water technique. The average daily metabolic rate (ADMR) (± 1 s.d.) for 24 individuals was 6.24 ± 1.17 cm³ CO₂/g/h, which corresponds to 95.3 ± 17.0 kJ/day (RQ = 0.75) for a bird of average mass (24.3 g).
There were no significant differences in daily energy expenditure between the sexes, nor between first-year and older birds. Individual males with longer tarsi had lower ADMR but raised larger broods. The ADMR increased at lower ambient temperatures, but this effect disappeared when the positive correlation with rainfall was taken into account. There was no relationship between the natural brood-size and parental daily energy expenditure. A positive correlation between ADMR and the time spent hopping and pecking suggests that foraging activity may account for some of the variability between individuals. The daily change in body-mass was not related to either the individual's age or its sex, and overall was not correlated with the level of daily energy expenditure. For birds examined on the same day, individuals with a higher ADMR had a greater loss of body-mass, which appears to be a high risk strategy. However, Wheatears also exhibited an ability to increase body-mass in conjunction with a drop in their daily energy expenditure.     

American alligator (Alligator mississippiensis) weight gain in captivity and implications for captive reptile body condition

The body condition of an animal is an indicator of health status and is dependent upon many factors, some of which can vary between wild and captive settings. Despite this, there have not been many studies on how captivity affects body condition relative to wild animal populations. This study explores the body condition of captive and wild American alligators (Alligator mississippiensis) because reptiles are frequently overlooked in studies of captive animal health and because alligators are well-represented in captivity. We collected body condition data from 209 captive alligators and 935 wild alligators throughout Florida and southeastern Georgia and compared the relationships between body condition and body length for each group. We found that captive alligators exhibited significantly higher body condition values as they aged, and that this result was driven by the difference between captive and wild males. Body condition values for captive juveniles did not differ from wild juveniles, but they differed when comparing adults. Our results suggest that factors such as diet and movement rates play major roles in determining alligator body condition and that body condition may be an important metric for monitoring captive alligator health, especially for older adult males.     

Blood values of Bald Ibis ( Geronticus eremita) in captivity: comparative ranges and variability with age, sex and physical condition

The Bald Ibis (Geronticus eremita) is one of the worlds most threatened species of birds. The number of individuals in captivity is several times greater than the number of individuals in the wild, so that the re-introduction of individuals from captive breeding into their natural habitat may be vital for the recovery of the species. A knowledge of the health problems associated with the handling of captive individuals and the improvement of their veterinary care could have great importance in determining the success of these captive breeding programs. Haematology and blood chemistry are very useful complementary tools in the diagnosis and treatment of diseases in birds, and provide valuable information about the individuals nutritional status and physical condition. The present work reports haematocrit and blood chemistry values for individuals belonging to a captive population of this species, and analyses their variability with respect to age, sex, and physical condition of the animals. Adults presented greater values of haematocrit, uric acid, total proteins, cholesterol, and aspartate amine transferase than the young. With respect to sex differences, adult female birds had higher concentrations of alkaline phosphatase than males, contrary to previous results for captive individuals of this species. The condition index of adults was positively correlated with triglycerides, glucose, and alkaline phosphatase levels, and negatively with urea and lactate dehydrogenase levels. These results may be very useful as a complementary diagnosis tool during the veterinary care of individuals of this species included in re-introduction programs.     

Urinary C-peptide as a method for monitoring body mass changes in captive bonobos (Pan paniscus)

In recent years methodological improvements have allowed for more precise estimates of nutrient intake in wild primates. However, estimates of energetic condition have remained relatively imprecise due to the difficulties of estimating digestive efficiency and energy expenditure in these animals. In the absence of a reliable intake-expenditure calculation, a method is needed that directly links changes in energetic condition, such as body mass, to physiological changes that can be detected via markers in body excretions such as urine or feces. One promising marker is C-peptide, a metabolic byproduct of insulin synthesis. Here we present the results of a food restriction experiment carried out in a group of captive bonobos (Pan paniscus). We measured changes in food availability and body mass and determined urinary C-peptide levels with the help of a time-resolved fluoroimmunoassay routinely used for measuring C-peptide in human blood. Urinary C-peptide levels decreased during a period of food restriction and increased again when food availability was continuously increased. During this refeeding phase an increase in body mass was significantly correlated with an increase in urinary C-peptide levels. Our results suggest that urinary C-peptide levels are an accurate indicator of individual energy balance. In conclusion, measuring C-peptide in urine is a promising method to quantify the energetic condition of wild apes.     

Intraspecies variation in avian energy expenditure: correlates and constraints

Data on energy expenditure by 553 individuals of 28 species of small bird (10–150 g) are presented. All estimates of energy expenditure were obtained using the doubly-labelled water technique. Intraspecies variation in daily energy expenditure was found to be positively correlated with brood provisioning rates, percentage of time flying and the frequency of non-resting activity. Correlations were also shown with body-mass, body-size and several environmental factors. Published data on basal metabolic rates (BMR) sometimes differed substantially from estimates either made specifically as part of the studies considered here or calculated from allometric equations. For the purpose of interspecific comparisons, specific estimates of BMR are to be preferred. When expressed as a function of BMR, energy expenditures of free-living birds ranged from 1 + to 7 + times BMR with a mode at 3 +. Values of daily energy expenditure exceeding 4 times BMR were found in up to 48% of species and 30% of individuals, so that, contrary to earlier suggestions, 4 times BMR is not a universal upper limit to the sustained work rate of small birds. Observed upper limits tended to be higher in species with energy-expensive foraging habits. Energy expended by breeding birds is likely to involve a balance between the benefits a greater expenditure has for offspring production and any fitness penalty associated with the high level of energy expediture which nest provisioning involves.     

Recovery from exhausting exercise in an Antarctic fish,Pagothenia borchgrevinki

Summary Pagothenia borchgrevinki, an Antarctic teleost fish was swum to exhaustion and changes in lactic acid levels and blood haematocrit were monitored during recovery. The fish did not perform well at high swimming speeds due to an inability of the white myotomal muscle to produce ATP by anaerobic glycolysis. Consequently, low levels of lactic acid were produced which were fairly rapidly broken down. Haematocrit values were low in non-exercised fish, and these increased by over 100% during exercise, falling back to control levels over many hours. This is probably related to the increased oxygen demand during exercise.     

Age and environment affect constitutive immune function in Red Knots (Calidris canutus)

We studied subspecies, age and environmental effects on constitutive immune function (natural antibody and complement titres, haptoglobin activity and leukocyte concentrations) in Red Knots (Calidris canutus). We compared C. c. islandica and C. c. canutus in the Wadden Sea and found no difference in immune function between subspecies. However, C. c. canutus on their wintering grounds in Banc d’Arguin had higher natural antibody and lower complement levels than C. c. canutus or C. c. islandica in the Wadden Sea. This suggests that immune function is determined more by the surrounding environment than by subspecies. We also compared age classes in the Wadden Sea and found that first year birds had significantly lower natural antibody levels than adults, but that second year birds no longer differed from adults. Finally, we examined the interaction of age and environment in Banc d’Arguin. We found that first year birds (but not adults) in a low quality habitat had higher leukocyte concentrations than first year birds or adults in a high quality habitat. Differences in available resources and defence needs between environments, and differences among individuals differentially distributed between sites, are likely important contributors to the variation in immune function we report. Future studies, which examine these factors on wild birds, will be important for our understanding of how animals function in their natural environment. (220).     

Blood chemistry and haematocrit of the black vulture (Aegypius monachus)

We determined the values of haematocrit and blood chemistry of the black vulture (Aegypius monachus) in Extremadura (Spain). We analysed 57 nestlings, five feral adults, seven captive individuals in their first year and five captive adults. Free-living adults had a higher haematocrit and lower calcium and alkaline phosphatases concentrations than captive birds. There were differences in haematocrit and in the concentrations of glucose, uric acid, total proteins, alkaline phosphatases, phosphorus and aspartate aminotransferase between nestlings and young in their first year and adults. The estimated age of the nestlings was significantly correlated with haematocrit, plasma glucose and total protein concentrations. The physical condition of nestlings was significantly correlated with plasma alkaline phosphatases levels.     

Blood levels of cyclic AMP, thyroxine, uric acid, certain metabolites and electrolytes under heat-stress and dehydration in the pigeon.

The effect of heat stress and dehydration on certain blood parameters were studied in the pigeon. Pigeons exposed to heat-stress and dehydration showed higher haematocrit values. Serum cyclic AMP levels, both with and without corrections made for difference in haematocrit, showed a more than two-fold increase in heat-stressed and dehydrated pigeons. Serum triglyceride level (before and after correction for haematocrit difference) in the experimental birds dropped to less than half that in the control birds. Total serum thyroxine (T4) did not show significant change in the experimentals (either with or without correction for haematocrit), although bound T4 and T3 index showed a statistically significant drop in the experimental group, after the correction for haematocrit. Total serum protein and albumin values after correction for haematocrit difference showed significant decreases in experimental birds. In pigeons exposed to heat-stress and dehydration, serum sodium increased while potassium dropped (with and without haematocrit correction). Heat stress and dehydration did not have any significant effect on serum levels of total cholesterol, uric acid, sodium, potassium, calcium and magnesium.     

Birds: blowin’ by the wind?

Migration is a task that implies a route, a goal and a period of time. To achieve this task, it requires orientation abilities to find the goal and energy to cover the distance. Completing such a journey by flying through a moving airspace makes this relatively simple task rather complex. On the one hand birds have to avoid wind drift or have to compensate for displacements to reach the expected goal. On the other hand flight costs make up a large proportion of energy expenditure during migration and, consequently, have a decisive impact on the refuelling requirements and the time needed for migration. As wind speeds are of the same order of magnitude as birds’ air speeds, flight costs can easily be doubled or, conversely, halved by wind effects. Many studies have investigated how birds should or actually do react to winds aloft, how they avoid additional costs or how they profit from the winds for their journeys. This review brings together numerous theoretical and empirical studies investigating the flight behaviour of migratory birds in relation to the wind. The results of these studies corroborate that birds select for favourable wind conditions both at departure and aloft to save energy and that for some long-distance migrants a tail-wind is an indispensable support to cover large barriers. Compensation of lateral wind drift seems to vary between age classes, depending on their orientation capacities, and probably between species or populations, due to the variety of winds they face en route. In addition, it is discussed how birds might measure winds aloft, and how flight behaviour with respect to wind shall be tested with field data.     

Antioxidant status in relation to age,condition, reproductive performance and pollution in three passerine species

Oxidative stress has been suggested as a mediator in life‐history trade‐off. By spending more resources on for example reproduction an organism might sacrifice its antioxidant defence. So far, most conclusions on trade‐offs between life‐history traits and oxidative stress have been drawn from laboratory studies using a few model species and there is a need for studies conducted in natural settings. We investigated associations between markers for antioxidant status (antioxidant enzyme activities and antioxidant levels), body condition, age and reproduction in three species of wild‐living passerines. The impact from an anthropogenic stressor (metal pollution) was also assessed. The three bird species showed interspecific variation in their SOD and CAT activities, indicating different pathways to eliminate radicals. The age of females affected both antioxidant status and the breeding performance, indicating the importance of age as a factor in life‐history studies. Old birds had lower levels of antioxidants/antioxidant enzyme activities and they produced larger broods/more successful broods, though the latter might be confounded by surviving females having increased fitness. Metal exposure had a negative impact on breeding, and improved breeding outcome was also associated with increased antioxidant defence, but metal exposure was not directly related to the oxidative status of birds, emphasizing that additional stressors might independently affect the same traits. Our results highlight that caution has to be taken when generalizing and extrapolating results to even closely related species. The results support the idea that there is a cost of reproduction, in terms of increased resources spent on antioxidant defence, though this should be confirmed with experimental studies.     

Haematocrit values in chinstrap penguins (Pygoscelis antarctica): variation with age and reproductive status

We studied haematocrit variation with age and reproductive status in chinstrap penguins (Pygoscelis antarctica) at Deception Island, South Shetlands. There was a significant difference in haematocrit values between different age groups (adults vs nestlings and juveniles). Adults had a higher haematocrit value than juveniles and nestlings and juveniles had higher haematocrit values than nestlings. There was also a significant difference in haematocrit values between adults of different status (breeding vs moulting). Breeding adults had higher haematocrit values than moulting adults. The observed differences between age groups were thought to be the result of different oxygen demands due to exercise. The observed differences between adults of different status could reflect the different demands associated with reproduction and moult fasting.