山地次生林破碎化对喜鹊繁殖功效的影响

Effect of Forest Patch Size on Reproductive Success of Magpies in Fragmented Secondary-forest

于 1999～ 2 0 0 0年春夏两季 ,在左家自然保护区及土门岭地区研究了破碎化山地次生林斑块面积对喜鹊 (Picapica)繁殖功效的影响。运用GPS定位系统确定了 12块大 (>2 0hm2 ,n =4 )、中 (10～ 2 0hm2 ,n =3)、小 (<10hm2 ,n =5 ) 3种类型的含喜鹊巢的次生林斑块及 2块毗邻的含喜鹊巢的连续分布次生林 (>2 0 0hm2 )对照样地 (每块面积 2 0hm2 )。观测了各斑块及对照样地中喜鹊产第 1枚卵的时间、窝卵数、平均卵重、出雏量及雏鸟出飞量等生态指标。结果表明 ,①斑块面积对喜鹊的繁殖功效存在着显著的影响 ;②喜鹊在对照样地和大面积斑块中的平均产卵时间早于小斑块中的 11 6 2d ;③对照样地和大面积斑块内的窝卵数略高于中、小面积斑块内 ,但差异不显著 ;④各斑块及对照样地中的平均卵重无显著差异 ,小面积斑块中的出雏率和雏鸟出飞率均最低 (5 1 17%和 4 2 88% ) ,大面积斑块中的出雏率最高 (72 12 % ) ,对照样地略次之 (71 93% ) ,对照样地中的雏鸟出飞率最高 (6 5 4 5 % ) ,大面积斑块次之 (6 2 71% ) ;⑤喜鹊在小面积次生林斑块中繁殖功效较低的主要原因是巢损失率较高。

The effect of forest patch size on reproductive success of Magpies ( Pica pica ) in fragmented secondary forests was studied in Zuojia Nature Reserve and Tumenling Area of Jilin Province from 1999 to 2000. 12 forest patches ranging in size from 3 5 to 46 6?hm 2 were located by using GPS, and classified as large (>20?hm 2, n =4), medium (10-20?hm 2, n =3) and small (<10?hm 2, n =5) patches. 2 control samples (20?hm 2) were selected in the extensive forest (>200?hm 2) being contiguous to those patches. The data on breeding success, laying date, clutch size, egg weight, brood size and fledged number of the Magpies were collected in 12 patches and 2 control samples. The results show that: ①the patch size influences the reproductive success signigicantly among forest categories; ②the mean laying date in the control samples and large patches is 11 62?d earlier than that in the small ones; ③the clutch size in the control samples and large patches is bigger than that in the small ones; ④the mean weight of eggs doesnt differ between all patches and control samples, but the hatching rate and fledgeling rate are the lowest in the small patches(51 17% and 42 88% respectively), the hatching rate is the highest in the large patches (72 12%) and a little lower in the control samples (71 93%), and the fledgeling rate is the highest in the control samples (65 45%) and next in the large patches (62 71%); ⑤the low reproductive success of the small patches in the secondary forests mainly caused by a high rate of nest failure.