Freezing heat: thermally imposed constraints on the daily activity patterns of a free‐ranging grassland bird

Abstract

Citation: Silva, J. P., I. Catry, J. M. Palmeirim, and F. Moreira. 2015. Freezing heat: thermally imposed constraints on the daily activity patterns of a free-ranging grassland bird. Ecosphere 6(7):119. http://dx.doi.org/10.1890/ES14-00454.1Abstract. Heat stress is a risk for birds exposed to high ambient temperatures, especially for those that live in open environments with limited protection from direct sun radiation. This makes them particularly vulnerable to climate warming. We studied how ambient temperature affects the daily activity of a threatened grassland bird, the little bustard Tetrax tetrax. The activity of 20 birds tracked by GPS satellite telemetry between 2009 and 2012 was monitored throughout the yearly cycle in the Iberian Peninsula. We found that temperatures over ;258C strongly inhibited the activity of birds during the breeding and postbreeding seasons. High temperatures were mostly frequent during mid-day, which often forced birds to reduce activity during this period, especially during summer. We show that the expected future rise in temperatures may result in a substantial reduction in the duration of the period of the day thermally adequate for maintaining activity. With climate change inactivity levels during breeding and post-breeding are expected to rise 37% and 59%, respectivly, compared to present standards. This may pose serious time constraints, particularly on functions like breeding and foraging, with potential consequences for individual fitness and population dynamics. Global warming may thus affect the range of birds not just through habitat change but also by limiting their activity.

The effects of scaling on age, sex and size relationships in Red-legged Partridges

“…Maturation begins once adult size is reached, and is complete by 12 months of age, after the completion of moult into adult plumage 49 , 50 . Previous research has focused on relating differences in animal size to geographical distribution, NPP, and global warming, because habitat factors exert a strong influence on animal size 51 – 54 . Our study was performed in a homogeneous habitat with seasonal changes in NPP, so that there is no influence of habitat on our data.…”

Feeling the heat: Elevated temperature affects male display activity of a lekking grassland bird

“…Accelerometer data were analysed for the period commencing two days after the loggers were fitted on the bird (to ensure normal behaviour was resumed) and ending when males left their territories for the first migratory movements (using GPS data collected by the dataloggers). Data collected between 21:00 hours and 5:00 hours were excluded from analyses, as birds display minimally at night [30]. Display behaviour was related to temperature in two classes of model at different temporal resolutions, (1) within days, using hourly measurements and (2) between days, using daily averages (see S1 Table for variable details).…”

“…The little bustard, Tetrax tetrax , is a lekking grassland bird that has been shown to reduce its overall activity at high temperatures in SW Iberia [30]. This area has some of the highest temperatures in Europe, and is also expected to be particularly affected by global warming and severe drought episodes by the end of the twenty-first century [31].…”

Changes in grassland management and linear infrastructures associated to the decline of an endangered bird population

“…The decline of the little bustard in Alentejo is probably not only a result of pressures occurring during the breeding season. In fact, multiple threats, such as loss of post-breeding and wintering areas, high anthropogenic mortality and global warming 40,67,68 , may be acting synergistically. Little bustards are short-distance migrants 69,70 that move towards more productive agriculture areas in northern, coastal or higher-altitude locations in Iberia during the dry summer season, in search of green vegetation 69,71 .…”