Abstract:Parental behavior and effort vary extensively among species. Life-history theory suggests that age-specific mortality could cause this interspecific variation, but past tests have focused on fecundity as the measure of parental effort. Fecundity can cause costs of reproduction that confuse whether mortality is the cause or the consequence of parental effort. We focus on a trait, parental allocation of time and effort in warming embryos, that varies widely among species of diverse taxa and is not tied to fecund… Show more
“…Yet, such arguments were predicated on the idea that genetically based physiological programs caused long development times by allocating relatively more intrinsic resources to physiological systems that enhanced longevity 2–4, 15 . Our results showing that long development times, as common in tropical birds 14, 26 , was a strong function of temperature rather than physiological programs raises questions about such perspectives.…”
Section: Discussionmentioning
confidence: 88%
“…2b, r
2 = 0.69, P = 0.005). Tropical species commonly have colder egg temperatures because of reduced time spent warming eggs by parents in the tropics 14, 26 . Consequently, embryonic periods of our tropical species with their colder normal egg temperatures exhibited stronger responses (steeper slopes) to heating compared with our north temperate species with warmer normal egg temperatures ( F
1,7 = 17.38, P = 0.004).Figure 2( a ) Correlation between measured differences in egg temperature, and incubation period differences between treatment and control among 42 paired nests belonging to nine species at two latitudes.…”
Section: Resultsmentioning
confidence: 99%
“…Yet, even species within the same order can differ dramatically (up to 7 °C) in the temperatures to which their embryos are exposed (Fig. 2b), because of differences in parental warming behavior 14, 26 . Such interspecific differences in embryonic temperatures are not restricted to birds 1 and can vary among diverse taxa as a function of parental choice of oviposition and nest sites, basking, and brooding behaviors 9, 12, 13 .…”
Section: Discussionmentioning
confidence: 99%
“…Thus variation in embryonic development time may reflect traditional expectations of genetically based physiological programs yielding small variation in development time within species, and larger differences among species. Alternatively, selection may instead act on evolution of parental behaviors (e.g., nest/egg site choice, warming behaviors) that affect embryonic temperature 9–14 . As a result, the differences in intraspecific and interspecific variation in development time may reflect relatively consistent embryonic temperature within species, and larger differences among species (Fig.…”
Section: Introductionmentioning
confidence: 99%
“…Tropical songbirds commonly have longer embryonic periods that are correlated with higher adult survival compared with north temperate species 14, 24 . This correlation may reflect the classic expectation of physiological benefits from slower growth and development yielding higher adult survival and longer life 25 .…”
The relative importance of intrinsic constraints imposed by evolved physiological trade-offs versus the proximate effects of temperature for interspecific variation in embryonic development time remains unclear. Understanding this distinction is important because slow development due to evolved trade-offs can yield phenotypic benefits, whereas slow development from low temperature can yield costs. We experimentally increased embryonic temperature in free-living tropical and north temperate songbird species to test these alternatives. Warmer temperatures consistently shortened development time without costs to embryo mass or metabolism. However, proximate effects of temperature played an increasingly stronger role than intrinsic constraints for development time among species with colder natural incubation temperatures. Long development times of tropical birds have been thought to primarily reflect evolved physiological trade-offs that facilitate their greater longevity. In contrast, our results indicate a much stronger role of temperature in embryonic development time than currently thought.
“…Yet, such arguments were predicated on the idea that genetically based physiological programs caused long development times by allocating relatively more intrinsic resources to physiological systems that enhanced longevity 2–4, 15 . Our results showing that long development times, as common in tropical birds 14, 26 , was a strong function of temperature rather than physiological programs raises questions about such perspectives.…”
Section: Discussionmentioning
confidence: 88%
“…2b, r
2 = 0.69, P = 0.005). Tropical species commonly have colder egg temperatures because of reduced time spent warming eggs by parents in the tropics 14, 26 . Consequently, embryonic periods of our tropical species with their colder normal egg temperatures exhibited stronger responses (steeper slopes) to heating compared with our north temperate species with warmer normal egg temperatures ( F
1,7 = 17.38, P = 0.004).Figure 2( a ) Correlation between measured differences in egg temperature, and incubation period differences between treatment and control among 42 paired nests belonging to nine species at two latitudes.…”
Section: Resultsmentioning
confidence: 99%
“…Yet, even species within the same order can differ dramatically (up to 7 °C) in the temperatures to which their embryos are exposed (Fig. 2b), because of differences in parental warming behavior 14, 26 . Such interspecific differences in embryonic temperatures are not restricted to birds 1 and can vary among diverse taxa as a function of parental choice of oviposition and nest sites, basking, and brooding behaviors 9, 12, 13 .…”
Section: Discussionmentioning
confidence: 99%
“…Thus variation in embryonic development time may reflect traditional expectations of genetically based physiological programs yielding small variation in development time within species, and larger differences among species. Alternatively, selection may instead act on evolution of parental behaviors (e.g., nest/egg site choice, warming behaviors) that affect embryonic temperature 9–14 . As a result, the differences in intraspecific and interspecific variation in development time may reflect relatively consistent embryonic temperature within species, and larger differences among species (Fig.…”
Section: Introductionmentioning
confidence: 99%
“…Tropical songbirds commonly have longer embryonic periods that are correlated with higher adult survival compared with north temperate species 14, 24 . This correlation may reflect the classic expectation of physiological benefits from slower growth and development yielding higher adult survival and longer life 25 .…”
The relative importance of intrinsic constraints imposed by evolved physiological trade-offs versus the proximate effects of temperature for interspecific variation in embryonic development time remains unclear. Understanding this distinction is important because slow development due to evolved trade-offs can yield phenotypic benefits, whereas slow development from low temperature can yield costs. We experimentally increased embryonic temperature in free-living tropical and north temperate songbird species to test these alternatives. Warmer temperatures consistently shortened development time without costs to embryo mass or metabolism. However, proximate effects of temperature played an increasingly stronger role than intrinsic constraints for development time among species with colder natural incubation temperatures. Long development times of tropical birds have been thought to primarily reflect evolved physiological trade-offs that facilitate their greater longevity. In contrast, our results indicate a much stronger role of temperature in embryonic development time than currently thought.
Many tropical species show declining populations. The pantropical order Trogoniformes has 76% of its species ranked as declining, reflecting a worldwide problem. Here, we report on the reproductive ecology and life history traits of the declining and near‐threatened old world Whitehead's Trogon (Harpactes whiteheadi), the declining new world Collared Trogon (Trogon collaris), and the stable Masked Trogon (T. personatus). We also reviewed the literature on reproductive ecology and life history traits of trogons to assess possible commonalities that might help explain population declines. We found that the declining Whitehead's and Collared Trogons had reasonable nest success (32% and 25%, respectively), while the stable Masked Trogon had poor reproductive success (9%), all contrary to population trends. However, the limited literature data suggested that poor reproductive success may be common among trogons, which may contribute to population declines. Parents fed young at a low rate and had long on‐bouts for incubation and nestling warming that reduced activity at the nest, as favored by high nest predation risk over evolutionary time. We found that young fledged from the nest with poorly developed wings, as also favored by high nest predation risk. Evolved nestling periods among trogon species suggests that poor wing development is likely common. Wing development has been shown to affect juvenile survival after leaving the nest. The poor wing development may be an important contributor to population declines that deserves more attention. Evolved life history traits are important to recognize as creating population vulnerabilities in a changing world.
For oviparous species such as birds, conditions experienced while in the egg can have long‐lasting effects on the individual. The impact of subtle changes in incubation temperature on nestling development, however, remains poorly understood, especially for open‐cup nesting species with altricial young. To investigate how incubation temperature affects nestling development and survival in such species, we artificially incubated American robin (Turdus migratorius) eggs at 36.1°C (“Low” treatment) and 37.8°C (“High” treatment). Chicks were fostered to same‐age nests upon hatching, and we measured mass, tarsus, and wing length of experimental nestlings and one randomly selected, naturally incubated (“Natural”), foster nest‐mate on days 7 and 10 posthatch. We found significant effects of incubation temperature on incubation duration, growth, and survival, in which experimentally incubated nestlings had shorter incubation periods (10.22, 11.50, and 11.95 days for High, Low, and Natural eggs, respectively), and nestlings from the Low treatment were smaller and had reduced survival compared to High and Natural nestlings. These results highlight the importance of incubation conditions during embryonic development for incubation duration, somatic development, and survival. Moreover, these findings indicate that differences in incubation temperature within the natural range of variation can have important carryover effects on growth and survival in species with altricial young.
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