Orioles are among the night-migrating birds. Like most temperate-zone birds, they begin their migrations because of the change in the length of daylight. For more than 35 years I have kept track of the spring arrival and the autumn departure of Baltimore orioles in the areas around Lake Minnetonka and throughout the Twin Cities. I have found that the first ones return on or close to May 1, and nearly all leave by the end of the first week of September. At some feeding stations, dozens of Baltimore orioles will come for sugar water or grape jelly on a day in late August or early September. And the next day, not a one. It seems quiet. We miss their orange and black colors but we also miss their songs and chatter.

Baltimore orioles winter in areas from southern Mexico to northern South America. Observers in Central America report that the first ones arrive during the second week of September, but the large influx does not come until month's end. There is almost no other winter bird visitant so widely and uniformly distributed throughout its wintering range. The oriole is an adaptable bird that makes itself at home almost anywhere trees and shrubs provide fruit and insects. They winter in arid areas or rain forests, on mountain sides and plantations. I have seen them wintering in Costa Rica.

Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.