Pre‐breeding energy requirements: thyroid hormone, metabolism and the timing of reproduction in house sparrows Passer domesticus

Abstract

M. 2003. Pre-breeding energy requirements: thyroid hormone, metabolism and the timing of reproduction in house sparrows Passer domesticus. -J. Avian Biol. 34: 298-306.We measured thyroid hormone (T3) levels and energy expenditure of pre-breeding house sparrows Passer domesticus in relation to the timing of breeding and reproductive success. The onset of reproduction was synchronised in two waves, separated by a three-week interval. On an annual basis, early breeders (birds that bred for the first time during the first wave) made significantly more breeding attempts, laid significantly more egg and raised 2.3 times more chicks to fledging than late breeders (birds that bred for the first time during the second wave). By the end of March, about one month before the first egg was laid in the population, plasma titres of testosterone in males and estradiol in females were still low and did not differ between early and late breeders. However, birds that subsequently bred early had higher titres of plasma triiodothyronine (T3) than birds that started to breed late. We show for the first time in a free-living bird population that Basal Metabolic Rate (BMR) is positively correlated with the plasma titre of T3. Differences in plasma T3 accounted for 48% of the inter-individual variation in BMR. Elevated T3 levels indicate that energy requirements increase prior to breeding. Although early breeding appears to be advantageous in terms of the number of offspring raised on an annual basis, the increased energy requirements prior to breeding are thought to delay the onset of reproduction in those birds that cannot afford the additional energy expenditure early in the season.O. Chastel (correspondence), A. Lacroix and M. Kersten, CNRS, UPR

Both thyroid hormone levels and resting metabolic rate decrease in African striped mice when food availability decreases

“…In contrast, other studies report no relationship between metabolic rate and thyroid hormones in captive mammals (Nilssen et al, 1984;Ostrowski et al, 2006), including humans (Bernstein et al, 1983;Johnstone et al, 2005). However, little information is available concerning the relationship between thyroid hormones and metabolic rate for animals living under natural conditions (exceptions are studies on birds: Chastel et al, 2003;Elliott et al, 2013;Welcker et al, 2013;Zheng et al, 2014; and a study of free-ranging Arctic ground squirrels Urocitellus parryii; Wilsterman et al, 2015), and the reported results are ambivalent. Some studies report a positive relationship between T 3 levels and metabolic rate (Chastel et al, 2003;Welcker et al, 2013) while others found no relationship (Burger and Denver, 2002).…”

“…However, little information is available concerning the relationship between thyroid hormones and metabolic rate for animals living under natural conditions (exceptions are studies on birds: Chastel et al, 2003;Elliott et al, 2013;Welcker et al, 2013;Zheng et al, 2014; and a study of free-ranging Arctic ground squirrels Urocitellus parryii; Wilsterman et al, 2015), and the reported results are ambivalent. Some studies report a positive relationship between T 3 levels and metabolic rate (Chastel et al, 2003;Welcker et al, 2013) while others found no relationship (Burger and Denver, 2002). This inconsistency in results highlights the need for additional studies examining the relationship between thyroid hormone levels and metabolic rate of free-living animals, especially mammals.…”

“…Additionally, there is a paucity of data concerning seasonal changes in the relationship between thyroid hormone levels and resting metabolic rate (RMR) or basal metabolic rate (BMR) in free-living animals because most studies examined both factors only during one season (i.e. the breeding season: Chastel et al, 2003;Elliott et al, 2013;Welcker et al, 2013). To our knowledge, seasonal variation in the relationship between thyroid hormone levels and metabolic rate has not been studied in freeliving mammals.…”

Thyroid hormones correlate with field metabolic rate in ponies,Equus ferus caballus

“…For example, it has been shown in humans that serum tT 3 concentrations increase with an elevated BMR, while no relationship between tT 4 and BMR could be established (Stenlöf et al, 1993). Furthermore, research in birds revealed a positive link between T 3 and BMR (Chastel et al, 2003;Welcker et al, 2013) as well as standard metabolic rate (BMR +thermoregulatory costs; Duriez et al, 2004). When we used resting f H as a proxy for BMR, our results indicated a relationship between BMR and TH, as seasonal changes in resting f H were positively correlated with seasonal changes in T 3 and negatively correlated with those of T 4 .…”

Reproduction and modulation of the stress response: an experimental test in the house sparrow

“…(a) Study species and population The study was carried out between March and July 2005 on a free-living population of house sparrows that breed in nest boxes in Chizé, France (46809 0 N, 0824 0 W; Chastel et al 2003). A large proportion of the adults used in this study were first captured during the pre-breeding period using mist nets and marked with a unique metal ring and colour combination.…”