Baltimore Oriole
| Scientific Name | Icterus galbula |
| Survival Strategy | Long-distance migrant |
| Arrival in Upper Midwest | Early May |
| Departure | Mid-August to early September |
| Destination | Central America and northern South America |
| Conservation Status | Least Concern |
Spring
In March, Baltimore orioles begin their trip north from the tropics, with migration reaching its peak in April and May. These brightly-colored birds arrive in the upper Midwest in early May. Nest building, followed by egg-laying, occurs in late May through mid-June. The female incubates 3 to 7 eggs for 11 to 14 days.
Summer
The chicks are born naked, blind, and helpless (altricial) and leave the nest 12 to 13 days after hatching. Parents will continue to feed the young for two weeks. Baltimore orioles begin the journey to the tropics in mid-August through early September.
Fall
Migration continues in September and October, with most orioles reaching their winter home in Central America and northern South America by November.
Winter
Most orioles are in social flocks in the tropics from December through January. A few stragglers will attempt to remain on the breeding grounds all winter, but they will likely not survive.
Behavior
Birds as Pollinators (The cool kids call it “ornithophily”)
Baltimore orioles are messy eaters when visiting flowers in search of sugary nectar. Unlike hummingbirds, orioles have short beaks and become covered in sticky yellow flower pollen. (Think about the last time you ate Cheetos® and ended up with the cheesy powder all over your clothes!) As the birds continue to feed, they unintentionally pollinate the flowers.
Nest Building
The female Baltimore oriole weaves a sock-shaped nest near the end of a branch, often nine meters (30ft) up in a deciduous tree. The nest, which must support the weight of three to seven eggs and the incubating female, is engineered from strands of plant fibers and discarded filaments of yarn, string, and weathered plastics.
The resulting creation rivals that of many contemporary textile artists. It is even more impressive knowing that an oriole weighs about as much as a light bulb and does not benefit from opposable thumbs. Still not impressed? Tape your thumbs to your hands, and then tie your shoes!
Physiology
Name Change “Do-Over”
The ranges of the Baltimore oriole (Icterus galbula) and Bullock’s oriole (Icterus bullockii) overlap in the Great Plains, and in this region, hybrids of these two species are common. For years biologists assumed that if a hybrid animal produced fertile young, it indicated that the parents were likely members of the same species. With this in mind, in 1973, ornithologists officially lumped the two birds into a single species, changing the name of both birds to “northern oriole.” For many birders and the city of Baltimore, Maryland, this was as traumatic as demoting Pluto to “dwarf planet” status.
Biologists used genomic sequencing and old-school field research to determine that the two species are not closely related. In 1995 the American Ornithologists Union reversed its 1973 decision and reinstated the original names; Baltimore oriole and Bullock’s oriole. After 22 years, Baltimore has its oriole back, while Pluto, on the other hand, is out of luck.
Diet
Baltimore oriels feed their young a diet dominated by high-protein soft-bodied insect larva during the breeding season. Adults eat invertebrates, including beetles, grasshoppers, crickets, and spiders. Oriels are not adapted for high-speed aerial pursuit and are limited to slow-flying insects such as butterflies and moths. As fruits such as mulberries, raspberries, and cherries come into season, oriels will not pass up the opportunity to eat their fill, much to the dismay of some gardeners.
Baltimore oriels are easily attracted to jelly feeders and, in peak season, are often responsible for a shortage of grape jelly in grocery stores.
During migration and in their winter range, oriels forage in flowering trees, feeding on nectar, fruits, and insects.
Lifespan and Mortality
Baltimore orioles can live up to 11 years in the wild.
Predators
Domestic cats kill adults Baltimore orioles. Predators of eggs or young orioles include American crows, blue jays, red squirrels, and eastern gray squirrels.
Climate Vulnerability
The range of the Baltimore oriole will shift slightly to the north and increase in area by about 15% in response to a warmer climate.
Never Stop Learning
Etymology: The genus Icterus comes from the Greek word “ikteros” for “jaundice.” The species “galbula” is the Latin word for “a small yellow bird.”
First Nations: The Ojibwe word for Baltimore oriole is “waabanoong bineshii.”
References
| Kennedy, S. 2001. “Icterus galbula” (On-line), Animal Diversity Web. Accessed February 15, 2022, at https://animaldiversity.org/accounts/Icterus_galbula/ |
| Rising, J. D. and N. J. Flood (2020). Baltimore Oriole (Icterus galbula), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.balori.01 |
| How Climate Change Will Reshape the Range of the Baltimore Oriole https://www.audubon.org/field-guide/bird/baltimore-oriole |
| November’s PolliNATION Pollinator of the Month: The Baltimore Oriole https://beyondpesticides.org/dailynewsblog/2017/11/novembers-pollination-pollinator-month-baltimore-oriole/ |
| Journey North: Baltimore Oriole https://journeynorth.org/oriole/ |
| From Northern Oriole to Baltimore and Bullock’s: A Split Decision https://journeynorth.org/tm/oriole/Baltimore-BullocksSplit_Rising.html |
| “Genomic and plumage variation across the controversial Baltimore and Bullock’s oriole hybrid zone” by Jennifer Walsh, Shawn M Billerman, Vanya G Rohwer, Bronwyn G Butcher, and Irby J Lovette, August 1, 2020, The Auk. DOI: 10.1093/auk/ukaa044. https://doi.org/10.1093/auk/ukaa044 |
| Ornithophily and Ornithophilous Flowers Bird Pollinators https://www.coastalwildscapes.org/resources/Documents/Education%20TAB/Presentations/Ornithophily.pdf |
| The Baltimore Oriole is Back https://www.nwf.org/Magazines/National-Wildlife/1994/The-Baltimore-Oriole-is-Back |
| Ojibwe names for Birds – Grand Portage National Monument (U.S. National Park Service) https://www.nps.gov/grpo/learn/nature/birds.htm |