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Migration and Annual Cycle
Baltimore and Bullock's Orioles

January

  • Baltimore orioles begin the new year in the tropics, mostly in social flocks that look like bright tropical ornaments in good feeding trees.
  • Bullock's orioles are soaking up the sun on their wintering grounds in Mexico, except the permanent residents of southern coastal California.

February

  • Baltimore orioles are on their wintering grounds in Florida, Central America, and the northern part of South America, with a handful usually in coastal California and occasionally a straggler or two survive the winter in the central or even northern states. Some are starting to migrate through Panama all through the month.
  • Bullock's orioles in southwestern California are there year-round, though the vast majority are down in Mexico.

March

  • Some migrating Baltimore orioles are reaching Mexico, while many are still found south to Panama.
  • Bullock's orioles are starting their migration through southern Arizona and California and up the coast. A few are starting to breed by month's end.

April
The peak of oriole migration, for Bullock's and Baltimore orioles both, occurs from mid-April through mid-May.

  • The first Baltimore orioles are reaching Texas, and by month's end, a few are reaching the central states.
  • Bullock's orioles are starting their migration through southern Arizona and California and up the coast. Breeding begins as soon as birds arrive.

May

  • Baltimore orioles reach the northern states and provinces. May is the peak month for nest-building.
  • Bullock's orioles finish their migration up the coast, and most reach their interior mountain and plains breeding grounds. Nesting peaks in May and early June.

June

  • This is the month most baby Baltimore orioles hatch. Parents are busy incubating eggs and raising babies.
  • Bullock's orioles are busy with eggs and babies. Baby-rearing peaks this month.

July

  • As Baltimore oriole babies become independent, parents begin molting their body and flight feathers, and some are already starting to migrate at the beginning of the month!
  • Bullock's orioles are still busy with babies in parts of their range, and also starting to molt their body feathers. Ornithologists are still collecting data about the molt of their flight feathers. They leave the drier areas of Washington and California by the end of the month.

August

  • Migration for Baltimore Orioles peaks in August and September. Birds are steadily molting their body and flight feathers.
  • Bullock's oriole migration peaks this month--few birds remain in the northern part of their range past August. Some birds are still molting.

September

  • Migration for Baltimore Orioles continues. Birds are still molting their body and flight feathers.
  • Bullock's oriole migration peaks continues. Some birds are still molting.

October

  • Migration for Baltimore Orioles in North America ebbs during the first half of the month, and most birds reach their tropical wintering grounds. Birds are done molting their body and flight feathers.
  • Bullock's orioles have just about all arrived on their wintering grounds in Mexico except the permanent residents of southern coastal California. Some are still molting.

November

  • Baltimore Orioles are mostly in the tropics, though a few individuals linger, even in the northern states and provinces. No one knows why some individuals are stragglers every year--most of these are seen in November and December, so ornithologists believe most of them end up dying as winter gets more severe.
  • Bullock's orioles are all on their wintering grounds in Mexico except the permanent residents of southern coastal California. They are done molting.

December

  • Just about all Baltimore orioles are in the tropics, but one or two stragglers might be seen on Christmas Bird Counts.
  • Bullock's orioles are on their wintering grounds in Mexico except the permanent residents of southern coastal California.
 

Baltimore Oriole Range Map | Bullock's Oriole Range Map

Range Map
Baltimore and Bullock's Orioles

 

 

 

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