Zhou et al. • NEST-SITE SELECTION AND NESTING SUCCESS OF THRUSHES 493 
2005), and rarely occupies small patches and forest 
edges (Deng et al. 2003, Deng and Gao 2005b). 
Global population size and trends have not been 
quantified, and the status of ‘Least Concern' was 
assigned by Birdlife International (Birdlife Inter 
national 2009) and IUCN. More detailed knowl¬ 
edge of the nesting ecology of the Grey-backcd 
Thrush would increase our understanding of the 
life history and breeding ecology of this species. 
We examined nesting habitat to empirically 
understand factors influencing nest-site selection 
and nesting success of Grey-backed Thrush at two 
scales, including nest-location (characteristics 
within the immediate vicinity of the nest) and 
nest-patch (characteristics of the habitat surround¬ 
ing the nest) (Martin and Roper 1988. Siepielski 
et al. 2001). Our objectives were to: (1) compare 
characteristics of Grey-backed Thrush nest sites to 
available habitats at the nest-patch scale, and (2) 
identify habitat attributes and nest-location char¬ 
acteristics (i.e., nest height, nest exposure) 
associated with nesting success. 
METHODS 
Study Area. —This study was conducted in the 
Dagang Forestry Farm (43° 34—41' N, 126" OS- 
14' E), an area of —12,000 ha of natural 
secondary forest fragmented by farmlands and 
scattered plantations in Jilin Province, China, 
from April to August 2008. The forestry farm 
extends from the eastern slope of the Changbai 
Mountains to the western edge of the Song-Liao 
plains (the northeastern plain of China). Conifer 
(Larin: spp.) plantations are managed for timber 
in the forest farm. All secondary forests are 
protected by the government, but unlawful forest 
thinning occasionally occurs. This region is in the 
temperate zone, and has a continental monsoon 
climate characterized by a cold (coldest in Jan 
with average temperature of - 18 to -20° C) and 
snowy winter, a windy spring and autumn, a hot 
(warmest in Jul with average temperature of 21- 
23 C) and humid summer (summer average 
rainfall = 434 mm), and only a short frost-free 
period (130-140 days) (Li 2007). 
Four plots were established with areas of —10. 
19. 38, and 54 ha, respectively, at least 500 m 
apart, and with an elevation range of 328 to 477 m. 
These plots were mainly covered by homogenous 
secondary deciduous forest of 50 to 60 years of 
age adjacent to farmlands and a few plantations. 
The dominant trees included Mongolian oak 
(Quercus mongolica), Pierot willow ( Salix pier- 
otii ), Dahurian birch ( Betula dahurica), Manchur¬ 
ian walnut (Juglans mandshurica), large leaf 
Chinese ash ( Fraxinus rhynchophylla ), and Japa¬ 
nese elm ( Ulmus japonica). Manchurian Schnei¬ 
der buckthorn ( Rhamnus schneideri), Chinese 
hawthorn ( Crataegus pinmlijida). Amur Maple 
(Acer ginnala ), Amur honeysuckle ( Lonicera 
maackii ), and Manchurian lilac ( Syringa retic¬ 
ulata) occupied the shrub layer in the study area. 
Narrow-leafed and broad-leafed herbaceous plants 
were the dominant life forms of ground cover. 
No regulations forbid human use of forests in 
the Dagang Forestry Farm, and economic activ¬ 
ities include cultivating maize and rice around the 
forest, raising and harvesting forest frogs in the 
forest, and grazing cattle. Some unpaved paths 
(> 2 m wide) have been created because of vehic¬ 
ular traffic related to grazing and farming. 
Data Collection—We systematically walked 
transect lines —8 m apart to search for nests of 
Grey-backed Thrushes within the plots from late 
April to early July 2008, and recorded the number 
of eggs or nestlings in each nest and whether it 
was successful or not. We revisited the nests every 
2-3 days. We conducted daily checks of nests in 
which nestlings were about to fledge and nests 
with eggs (or nestlings) that disappeared or failed 
to hatch on the expected day. Nests were 
considered successful when the nestlings (at least 
1) disappeared at the expected time of fledging (± 
1 day). We considered nests to have failed when 
eggs disappeared, nests were demolished, or 
nestlings were absent before their expected 
fledging dale (Hoover and Brittingham 1998, 
Aguilar et al. 2008). 
We collected vegetation data at each nest site 
during July and early August. Nest-site character¬ 
istics, including nest-location and nest-patch data, 
were measured in a 0.04-ha circle (11.3-m radius) 
centered on the nest, using a modified version of 
Noon (1981), as described by Chu and Zheng 
(1993). Diameter at breast height (DBH) of the 
nest tree was recorded as well as nest height (m), 
distance from Lhe nest to the main stem of the nest 
tree (cm), and exposure ( ) for each nest location 
(Table 1). 
The exposure of each nest was evaluated with a 
modified version of a method described by 
Hoover and Brittingham (1998). We painted 10 
red circles 5 cm in diameter, 6 cm apart from each 
other, in two rows of five on a white cover board. 
The cover board was placed directly facing east, 
south, west, and north, respectively to calculate 
