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Richdale 's main ornithological interest was in seabirds , especially penguin s and petrel s , and he was engaged in long-term studies of various species for most of his life .
 Richdale
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Richdale