7540
Survival of prefledgling gulls was poor , with only 0 . 68 and 0 . 5 chicks per nest surviving to three and four weeks after hatch , respectively .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None