Environmental Temperature Affects Prevalence of Blood Parasites of Birds on an Elevation Gradient: Implications for Disease in a Warming Climate

Background: The rising global temperature is predicted to expand the distribution of vector-borne diseases both in latitude and altitude. Many host communities could be affected by increased prevalence of disease, heightening the risk of extinction for many already threatened species. To understand how host communities could be affected by changing parasite distributions, we need information on the distribution of parasites in relation to variables like temperature and rainfall that are predicted to be affected by climate change.\ud \ud Methodology/Principal Findings: We determined relations between prevalence of blood parasites, temperature, and seasonal rainfall in a bird community of the Australian Wet Tropics along an elevation gradient. We used PCR screening to investigate the prevalence and lineage diversity of four genera of blood parasites (Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma) in 403 birds. The overall prevalence of the four genera of blood parasites was 32.3%, with Haemoproteus the predominant genus. A total of 48 unique lineages were detected. Independent of elevation, parasite prevalence was positively and strongly associated with annual temperature. Parasite prevalence was elevated during the dry season.\ud \ud Conclusions/Significance: Low temperatures of the higher elevations can help to reduce both the development of avian haematozoa and the abundance of parasite vectors, and hence parasite prevalence. In contrast, high temperatures of the lowland areas provide an excellent environment for the development and transmission of haematozoa. We showed that rising temperatures are likely to lead to increased prevalence of parasites in birds, and may force shifts of bird distribution to higher elevations. We found that upland tropical areas are currently a low-disease habitat and their conservation should be given high priority in management plans under climate change

Oxidative Stress Mediates Physiological Costs of Begging in Magpie (Pica pica) Nestlings

[Background] Theoretical models predict that a cost is necessary to guarantee honesty in begging displays given by offspring to solicit food from their parents. There is evidence for begging costs in the form of a reduced growth rate and immunocompetence. Moreover, begging implies vigorous physical activity and attentiveness, which should increase metabolism and thus the releasing of pro-oxidant substances. Consequently, we predict that soliciting offspring incur a cost in terms of oxidative stress, and growth rate and immune response (processes that generate pro-oxidants substances) are reduced in order to maintain oxidative balance. [Methodology/Principal Findings] We test whether magpie (Pica pica) nestlings incur a cost in terms of oxidative stress when experimentally forced to beg intensively, and whether oxidative balance is maintained by reducing growth rate and immune response. Our results show that begging provokes oxidative stress, and that nestlings begging for longer bouts reduce growth and immune response, thereby maintaining their oxidative status. [Conclusions/Significance] These findings help explaining the physiological link between begging and its associated growth and immunocompetence costs, which seems to be mediated by oxidative stress. Our study is a unique example of the complex relationships between the intensity of a communicative display (begging), oxidative stress, and life-history traits directly linked to viability.GM-R was supported by the Spanish Government (Ministerio de Ciencia y Tecnología, “Juan de la Cierva” program), and TR was supported by the Consejo Superior de Investigaciones Científicas (CSIC; Proyectos Intramurales Especiales)

Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds

The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and urbanization remain to be determined. We propose that effects of food abundance or quality, temperature, noise, pollution, or disturbance by humans may on their own or in combination affect laying date and/or clutch size

Variation of adult Great Tit Parus major body condition and blood parameters in relation to sex, age, year and season

In recent years, an increasing number of studies have focused on the ranges of variation of health related biochemical and haematological parameters in wildlife, but information is still scarce for enzymatic activities which can be extremely important in detecting potential responses to environmental change. In a Great Tit (Parus major) population, we describe the variation in relation to age, sex, season and year of: (1) morphological: body condition index, fat and muscle, (2) haematological: hematocrit, haemoglobin, white blood cell count and heterophil/lymphocyte ratio, and (3) biochemical parameters: plasma protein and activities of plasma cholinesterases (acetylcholinesterase and butyrylcholinesterase) activity and red blood cell glutathione peroxidase. Sex had significant effects on all morphological parameters except fat. Age significantly affected cholinesterase activities, H/L ratio and haemoglobin, and there was a significant interaction between sex and age affecting hematocrit. There were significant interactions of year and season affecting almost all parameters studied - body condition index, fat, protein, acetyl and butyrylcholinesterase activities, glutathione peroxidase activity and haemoglobin. This study indicates that these parameters are largely influenced by year and seasonal effects, besides the individual's intrinsic variation. Therefore, when evaluating experimental or environmental change effects, appropriate controls should be used. © Dt. Ornithologen-Gesellschaft e.V. 2009

HEALTH-STATE VARIABLES AND ENZYMATIC BIOMARKERS AS SURVIVAL PREDICTORS IN NESTLING GREAT TITS (PARUS MAJOR): EFFECTS OF ENVIRONMENTAL CONDITIONS

The health state of nestlings can be a useful bioindicator of the quality of the environment in which they are reared, but, to enable detection of responses to environmental change, the variation of health parameters under natural conditions should be evaluated. We describe the variation of morphological, biochemical, and hematological variables in relation to time of sampling, hatching date, brood size and type, and year in nestlings of two populations of Great Tits (Parus major) in Choupal, Portugal, and Wytham, United Kingdom. The influence of these health variables on nestlings' survival to first winter and recruitment into the breeding population was assessed in Wytham. Variation in plasma protein, total plasma cholinesterase (ChE), and acetylcholinesterase activities reflected circadian rhythms. Hatching date affected total plasma ChE and butyrylcholinesterase (BuChE) activities, and levels of red-blood-cell hemoglobin (Hb) and hematocrit (HCT). In Choupal, HCT increased with brood size. Nestlings in Choupal had significantly lower protein and Hb levels, and higher glutathione peroxidase (GSH-Px) activity, during a drier year. Second-brood nestlings had significantly lower levels of Hb and HCT. Of the studied variables, only plasma BuChE and red-blood-cell GSH-Px activities were related to nestlings' survival to first winter and recruitment. © 2008 by The American Ornithologists' Union. All rights reserved

PHYSIOLOGICAL CONDITION AND BREEDING PERFORMANCE OF THE GREAT TIT

The energy expenditure associated with breeding may have detrimental effects on the breeder's physiology. Some studies have focused on the relationship between breeding performance and health status, but information on the link with biochemical variables reflecting susceptibility to oxidative stress is scarce. Over two years (2005 and 2006), using several morphological, biochemical and hematological variables, we measured the association between several measures of breeding (laying date, clutch size, mean egg weight, brood size, number of fledglings, and mean weight before fledging) and health in the Great Tit (Parus major). The effect of raising a second brood on the breeders' physiological condition was also studied. females' body-condition index tended to be positively correlated with breeding performance, whereas in males the correlation was negative. females laying later had lower hematocrits and higher glutathione peroxidase activity (GSH-Px), and those raising larger broods had also higher GSH-Px activity and tended to have lower plasma protein. The effect of raising a second brood was reflected mostly in body reserves but varied by sex. Our study suggests that trade-offs between breeding activity and physiological condition of the sexes differ and that hematocrit and GSH-Px are sensitive indicators of the physiological condition of breeding females. © Cooper Ornithological Society 2010

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