Incubation strategies of the Black-necked Crane (Grus nigricollis) in relation to ambient temperature and time of day

Abstract

Background:The behavior of cranes reflects many of their survival strategies, but little has been known of the incubation strategies of cranes, in which both parents share incubation duties, in response to cold temperatures in alpine environments. The lack of information may restrict the effective conservation of the threatened Black-necked Crane (Grus nigricollis), a biparental bird nesting in high elevation wetlands. Methods:We directly observed and used infrared video cameras from 2014 to 2015 to study the incubation behavior and quantitatively measured the frequency and details of egg turning behavior in the Black-necked Crane at the Yanchiwan National Nature Reserve in western Gansu Province, China. Results:At lower ambient temperatures in the morning, crane parents spent more time on the nest with less recess frequency and prolonged on-bout duration, while at higher temperatures around noon, the parents had more frequent recesses from incubation and shorter periods between nest exchanges. They adjusted the amount of time incubating by varying the recess frequency and the length of on-bout duration. Mean nest attendance and egg turning frequency of females were significantly higher than those of the males. The nest attendance and on-bout duration of females showed a significantly negative relationship with those of males. The two parents responded differently to the change of temperature. Females spent more time on the nest at lower morning temperatures, while males increased their time on the nest at higher temperatures after noon. Higher incubation recess frequency and egg turning frequency were observed at noon, probably because parents spent more time foraging, taking advantage of the lower egg cooling rate. Conclusion:Both Black-necked Crane parents in the alpine environment adjusted their behavior in response to the thermal requirements of eggs and the weather conditions experienced. Our findings demonstrate that parents of this species incubated in different but complementary ways and efficiently enhanced egg care in a dynamic environment, so as to maximize benefits from the warm portion of the day and the intense solar radiation while minimizing the cost of rewarming eggs and the risks of cooling eggs.

Critical reproductive behaviors in Scaled Quail and Northern Bobwhite are affected by thermal variability and mean temperature

“…These findings further suggest that the timescales we use to measure thermal change and behavioral modification alter how we view the plasticity of organismal behavior to the thermal environment. Multiple studies have shown that the relationship between temperature and the average lengths of off-bouts predicts avian reproductive success (48–51). Approaches considering averaged conditions can contextualize general trends in behavior (52,53), but as we show above, only examining behavior in this way risks missing the relationship between the rate of thermal change and organismal behavior.…”

Factors influencing Cinnamon Teal nest attendance patterns

“…In arid climates such as in the San Luis Valley of Colorado, temperatures can vary by more than 20 °C throughout the day (Mix et al 2011). Daily variation in temperature has been shown to influence nest attendance patterns in other bird species including Wild Turkeys Meleagridis gallopavo (Spohr 2001), Black‐necked Cranes Grus nigricollis (Zhang et al 2017) and Carolina Chickadees Poecile carolinensis (Walters et al 2016). In addition, eggs become increasingly susceptible to fluctuations in temperature as they approach hatching, necessitating increased attentiveness or strategic timing of nest recesses to correspond with high ambient temperatures (Romanoff & Romanoff 1949, Hepp et al 2005, Burnam et al 2012).…”

Autumn migration of black‐necked crane (Grus nigricollis) on the Qinghai‐Tibetan and Yunnan‐Guizhou plateaus

“…The black-necked crane (Grus nigricollis; Figure 1), the only alpine crane species endemic to the plateaus, primarily breeds in scattered sites on the Qinghai-Tibetan Plateau in south-central China (Archibald et al, 2020), and winters in southern and eastern parts of the plateau (Bishop et al, 1998;Jia et al, 2019), and on the Yunnan-Guizhou Plateau in China (Archibald et al, 2020;Li, 2014;Zhang et al, 2014). The species has recently been reclassified from "Vulnerable (VU)" to "Near Threatened (NT)" by the International Union for Conservation of Nature (IUCN, 2020) due to recent growth in its population, with an estimated global population of 17,389-17,610 in the wild (Chen et al, 2023).…”