| Birds plays an important role urban ecosystem. With the accelerated pace of urbanization, its impact on the ecosystem, especially on birds have drawn much attention. In order to explore the response of birds to urbanization, we choose Hangzhou city area as study site and the Chinese Bulbul(Pycnonotus sinensis)-one of the most common bird in Hangzhou-as the object species to explore the response of Chinese Bulbul in life history characteristics to urbanization. We compared date of beginning nesting, clutch size, egg weight, incubation period, fledging period, hatching success and fledging rate of234nests from countryside to city center. Percentage of concrete surface within a series of buffer zone was used to measure urbanization gradient. During fledging period, we use miniature camera records the type of food and food delivery rates, and after the fledging period we conduct artificial nest predation experiment by placing simulation egg. The results are as following:(1) Totally, we monitored234nests of breeding Chinese Bulbul nests in two years. The Chinese Bulbuls first be seen carrying nest material on March25. The earliest laying egg were record in April1st, the latest laying egg was June21. Egg laying concentrated from April15to May10. There was a significant negative correlation between start breeding time and urbanization Index, indicating that with the increased of the degree of urbanization Chinese Bulbul start breeding significantly earlier (n=101, P <0.001).(2) The average clutch size was3.31±.47(n=207), and it did not have a linear relationship with urbanization index, indicating that Chinese Bulbul had an significant difference in cluth size between urban and rural environments.(3) Mean long radius of eggs was22.02±1.74mm (n=84), and short radius was16.37±1.10mm (n=84), and the average egg weight were3.10±0.24g (n=84). There was no significant correlation between eggs’long radius and short radius with urbanization index, whereas the average eggs weight has a significant positive correlation with urbanization index, indicating that breeding nests in urban habitat had a higher average egg weight (n=84, p<0.01).(4) Mean incubation period was11.37±0.84d (n=84), and hatching success rate was65.01%(n=220). The incubation period did not have a linear relationship with urbanization index, whereas hatching success rate showed a significant positive linear correlation with the urbanization index (n=157, p=0.028),which meant that nests in urbanization habitats had a higher hatching success rate.(5) The average fledging period was11.80±1.15d (n=96), and fledging rate52.32%(n=163). The Fledging period had significant positive linear correlation with urbanization index which meant that nests in urban habitat had a longer fledging period. Fledging rate did not have a significant linear correlation with urbanization index, indicating that there was no significant difference in fledgling mortality between city and natural environment.(6) The total breeding success rate is33.69%(n=226). There is no significant correlation between the total reproductive success and urbanization index, which means in different urbanization gradient, Chinese Bulbul’s total breeding success had no significant difference.(7) Results of nestling food delivery rate showed that the higher urbanization index the higher food delivery frequence per hour (n=78, P=0.001), implied that urban environment does not lack of food.(8) The ratio of artificial food showed a significant positive correlation relationship with urbanization index, indicating that as the degree of urbanization increased, the proportion of artificial food significant increased (n=24, P=0.040).(9) For adult birds, the urban environment does not seem to lack of food, so they can get enough food, has a higher egg weight, start reproduction early and thus get a longer reproductive period.However, the changes of food resource, especially the increaseing of artificial food proportion had a negative effects to the nestlings which resulted in a prolonged brood period.(10) The results of egg predation in the suburban showed that the higher urbanization index the lower egg predation (n=133, p=0.024). The results of egg predation experiments showed that17predated nests (n=54) all occurred in the suburban area. According to the data of infrared camera video and prey traces from the artificial eggs, the major egg predators were Red-billed Blue Magpie,(Urocissa erythrorhyncha), squirrels and rodents. Different predators along urban gradient led to different nest predation pressure. |
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