英文關鍵字
americas
animals
bank
birds
branch
breeding
burrowing
cliff
collared
colony
common
environment
europe
european
fauna
flight
fly
hirundinidae
holes
insectivorous
known
lake
martin
michigan
migrating
migratory
natural
nature
nesting
ornithology
outdoor
passeriformes
passerine
plumage
riparia
riverside
sand
scene
season
shore
spring
swallow
swallows
tree
tunnel
wall
wild
wilderness
wildlife