Shifts in foraging behavior of wintering Hooded Cranes (Grus monacha) in three different habitats at Shengjin Lake, China

Abstract

Background: Wetland loss and degradation result in a reduction in the availability and quality of food for wintering waterbirds. Birds normally modify their foraging behavior to adapt to variations in food availability. In this study, we compared shifts in foraging behavior of Hooded Cranes (Grus monacha) in three different habitats at Shengjin Lake, China to understand the response of these cranes to changes in habitat. Methods:We investigated the food density and foraging behavior of Hooded Cranes in Shengjin Lake National Nature Reserve from November 2014 to April 2015. We used regression equations to describe the changes in food density. A total of 397 behavioral observations were used in the analyses of their foraging efforts. We fitted a candidate set of generalized mixed linear models to analyze the relationship of foraging efforts and food density. We used a method of information theory to guide the selection of the model and Akaike's Information Criterion to calculate the value of each model. The relationship between food density, disturbances and foraging behavior was illustrated using a generalized linear model. Results:Along with the temporal variation and exploitation of food biomass, the food density varied widely among foraging sites. During the early winter period, foraging efforts were more pronounced in the paddy fields and meadows but not significantly different among the three habitats. The cranes spent more foraging effort in the paddy fields and meadows during the middle stage and in the meadows and mudflats during the late winter. The results of the generalized linear model showed that food density and disturbances had different effects on the rate of foraging success during the winter, while the effect of foraging effort was not significant. Furthermore, the rate of feeding success was markedly affected by disturbances in the paddy fields. The combined action of food density and disturbances had a significant effect on the rate of foraging success in the meadows, while the effect of foraging effort was also not significant in three habitats. Conclusions:Changes in foraging behavior were significant in three habitats, which were affected by food density and disturbances. The rate of foraging success increased in the habitat with low food density and low disturbances to increase the foraging efficiency in the lake. With abundant food and a high level of disturbance, the rate of foraging success decreased to ensure more secure access to food.

Significant Differences in the Gut Bacterial Communities of Hooded Crane (Grus monacha) in Different Seasons at a Stopover Site on the Flyway

“…Shengjin Lake is a shallow lake in the middle and lower Yangtze River floodplain [18], and one of the largest wintering grounds in the world. The main food resources for hooded cranes are Vallisneria natans, Potamogeton malaianu, and rice grains [19]. In addition, the abundance and availability of food can influence the foraging strategies of the hooded crane, which may affect their intestinal physiology and ecology [20].…”

Do Geese Facilitate or Compete with Wintering Hooded Cranes (Grus monacha) for Forage Resources?

“…It also reflected the distribution of daily energy requirements and behavioral patterns, showing that the hooded cranes were more flexible to responding to changes in food density. At the same time, no correlation was seen between foraging success rate and foraging effort [25]. Relative flock size was defined as the proportion of individual hooded cranes compared to the number of geese in the same foraging habitat at a given time.…”

Flexible Foraging Response of Wintering Hooded Cranes (Grus monacha) to Food Availability in the Lakes of the Yangtze River Floodplain, China

“…These constraints constitute an important ecological problem for species, with factors other than food also likely altering the foraging behavior of animals [12]. Given these constraints, animals have likely developed flexible foraging strategies to optimize the benefits of foraging to facilitate survival, and they are able to respond to the complex environment in a timely manner and adjust their foraging behavior to attempt to consume food resources that offer the greatest energy gain at the least cost [13][14][15]. Waterbirds, in particular, must display flexibility due to the constantly changing water levels of wetlands, as well as the management of agricultural lands (such as paddies) [13,[16][17][18][19][20].…”

“…Given these constraints, animals have likely developed flexible foraging strategies to optimize the benefits of foraging to facilitate survival, and they are able to respond to the complex environment in a timely manner and adjust their foraging behavior to attempt to consume food resources that offer the greatest energy gain at the least cost [13][14][15]. Waterbirds, in particular, must display flexibility due to the constantly changing water levels of wetlands, as well as the management of agricultural lands (such as paddies) [13,[16][17][18][19][20]. Migratory waterbirds display flexibility in foraging behaviors, e.g., dunlin have changed their foraging mode, as well as morphological and digestive strategies, in response to changes in environmental conditions [21,22].…”

“…The Hooded Crane (Grus monacha Temminck, 1835) is a typical large migratory bird species that is classified as vulnerable (VU) in the revised Red List of the International Union for Conservation of Nature (IUCN), with a global population of approximately 11,600 individuals [13]. Three sub-populations breed in the tundra and floodplains of eastern Siberia and northeast China [32,33].…”