Resource levels, reproduction and resistance to haematozoan infections

Abstract

Compromise of immune function during reproduction may form a link between parental e¡ort and the cost of reproduction, but the role of environmental variation in structuring intra-individual life-history trade-o¡s has been poorly investigated. We manipulated the need for parental e¡ort in Eurasian kestrels, Falco tinnunculus, by food-supplementing broods for three nestling periods, during which the natural main food supply (voles) varied, and found that parental parasitaemia was inversely related to yearly vole densities. The level of parasitaemia in females was, however, reduced by food supplements. No e¡ect on males was expected, as earlier work has shown that only females responded to the supplements by changing their behaviour. We show directly that the likelihood of female parasitaemia was diminished by spending less time in £ight-hunting, which was related to reproduction during a good vole year, to our supplementary feeding, and to being mated to a male with high parental e¡ort. Our results represent a novel direct bene¢t for females in resource-providing species, linked to female as well as o¡spring, wellbeing, and they provide insight into why the appearance of reproductive costs may be linked to gender or environmental conditions.

Predator avoidance and immune defence: costs and trade–offs in snails

“…Deerenberg et al 1997;Nordling et al 1998;Siva-Jothy et al 1998;Wiehn & KorpimÌki 1998). Together, these observations suggest that some behaviours may have indirect ecological costs in terms of reduced immunocompetence and a greater risk of pathogenic infection.…”

Experimentally activated immune defence in female pied flycatchers results in reduced breeding success

“…Among the birds breeding in the centre area close to the copper smelter, vaccinated females were less likely to regrow removed tail feathers than control ones, but there was no di¡erence in £edging success between female treatment groups. Although any trade-o¡ between immune defence and reproduction can be expected to be more pronounced under stressful rather than benign conditions (Wiehn & KorpimÌki 1998;Ilmonen et al 1999;Wiehn et al 1999), the exceptionally rainy breeding season in 1998 (see ½ 2) may have made the conditions bad enough for birds breeding in the background area. However, near the smelter the e¡ects of our immune challenge were apparently overridden by stronger e¡ects of heavy metal pollution on nestling mortality.…”

Nutrient partitioning between reproductive and immune functions in animals

“…An increased food supply (voles, Microtus agrestis) resulted in a decreased level of parasitism in nestling owls such as tawny owls (Strix aluco; Appleby et al 1999) and in kestrels (Falco tinnunculus; Wiehn & Korpimaki, 1998). An increased brood size resulted in an increased prevalence of haematozoan parasites in great tits (Parus major; Norris et al 1994;Richner et al 1995), and reduced ability to mount an antibody response to Newcastle disease virus vaccine in the collared fly catcher (Ficedula albicollis; Nordling et al 1998).…”