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