English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Spending the winter in northern climes with short days and cold ambient temperatures (T a ) can be energetically challenging for small birds that have high metabolic and heat loss rates. Hence, maintaining body temperature (T b ) in T a below thermoneutrality can be energetically costly for a small bird. We still know little about how increased heat production below thermoneutrality affects the level at which T b is maintained, and if these patterns are age specific. To test this, we measured subcutaneous body temperature (T s ) and resting metabolic rate (RMR) simultaneously in blue tits (Cyanistes caeruleus) during winter nights in T a 's ranging from 25 to - 15 °C. RMR increased below the lower critical temperature (LCT, estimated at 14 °C) and was 6% higher in young (birds in their first winter) compared to old birds (birds in their second winter or older). The higher RMR was also mirrored in higher T s and thermal conductance (C) in young birds, which we suggest could be caused by age differences in plumage quality, likely driven by time constraints during moult. Reduction in nightly predicted T b was modest and increased again at the coldest ambient temperatures, suggesting that either heat retention or heat production (or both) improved when T a reached levels which are cold by the standards of birds in our population. Our results show that levels of heat production and T b can be age specific. Further studies should address age-specific differences on quality, structure, and thermal conductivity of plumage more explicitly, to investigate the role of variation in insulation in age-linked metabolic phenotypes.

Age differences in night-time metabolic rate and body temperature in a small passerine