Orioles are brightly colored birds that arrive in many parts of North America in the spring to breed. Their arrival is a sign that winter is over and summer is coming. But do orioles stick around all summer, or do they leave once breeding season is over? Here’s a look at the behavior of these beautiful birds throughout the summer months.
When do orioles arrive in the spring?
Orioles usually arrive at their breeding grounds anywhere from mid-March to early May depending on the region and the weather conditions in a given year. The males tend to arrive first to establish breeding territories. Females arrive a week or two later.
In the Midwest and Mid-Atlantic regions, orioles often arrive in April. Farther south, they may arrive as early as late March. On the West Coast, they may not show up until May.
The earliest recorded arrival dates for two common oriole species are:
- Baltimore Oriole: March 15 (Arkansas)
- Bullock’s Oriole: April 7 (California)
Do the same orioles return each year?
In many cases, the same male orioles do return to the same breeding sites year after year. Female orioles are less likely than males to return to the same site.
Young orioles hatched the previous summer typically do not return to their place of birth the following spring. Instead, they migrate north and settle elsewhere.
Banding studies have shown that male Baltimore Orioles have high site fidelity. One study in Wisconsin found that 80% of banded male Baltimore Orioles returned to the same park the following year. Another study found that the oldest recorded Baltimore Oriole in the wild was 11 years old.
When does breeding season start?
Orioles begin breeding almost immediately after arriving at their summer grounds. The males sing melodious, warbling songs to establish territories and attract females.
Courtship may start within days of arrival. Pairs construct a hanging pouch nest about one week after pairing up. The female then lays 3-7 eggs and incubates them for 12-14 days while the male brings her food.
Here are some typical breeding/egg laying dates for two common oriole species:
- Baltimore Oriole: Mid-May to early June; sometimes late April in the south
- Bullock’s Oriole: Mid-May to early June
The nesting period lasts 6-8 weeks as the female incubates the eggs and cares for hatchlings. The male continues to supply most of the food during this time.
How many broods do orioles have?
Orioles typically raise one brood per breeding season, with anywhere from 3-7 young hatching in each nest. However, they may sometimes raise two broods in a season.
Second broods are more common in the southern part of their range where the breeding season is longer. In one study of Baltimore Orioles in Arkansas, about 15% of females raised two broods.
Factors like an abundant food supply and a prolonged spring/summer season may increase the chances of a female raising a second brood.
Do the parents stay with the young?
Both male and female orioles feed and care for the young, which remain in the nest for 12-14 days after hatching. The female broods and feeds the nestlings while the male brings food to the nest.
The young fledge from the nest at 14-18 days old but cannot fly well at first. The parents continue caring for the fledglings for 2-3 weeks as they teach them to forage on their own. By 4 weeks after leaving the nest, the young are independent.
So the adult male typically spends 8-10 weeks attending his mate and young during breeding season. The female may spend closer to 3 months focused on her nest if she raises two broods.
Do orioles stay all summer?
The breeding season keeps orioles busy from spring through summer. But some individuals, mainly males, do remain on their breeding grounds all summer long.
However, there is a southward migration movement that starts in mid-summer after breeding. Some of the key points about oriole summer residency include:
- Adult males tend to remain on territory throughout summer
- Females and immature birds are more migratory
- Females may leave breeding grounds as early as late June
- Immatures migrate earlier than adult females
- Southward migration peaks in August but continues into September
- A few orioles may linger into October in the north
The occasional oriole may stick around a specific backyard all summer if there is a ready food source. But overall populations decline after breeding season as migrants move south.
What do orioles eat in summer?
Orioles are fruit eaters during summer, enjoying berries and other fleshy fruits. They use their pointed beaks to puncture the skin of fruits and feed on the juicy contents.
Some of their favorite summer fruits include:
- Raspberries
- Blackberries
- Cherries
- Mulberries
- Figs
- Elderberries
Orioles get much of their moisture from fruit. They also drink nectar from flowers and feed insects to their young. Caterpillars are an important food source during breeding season.
Here is a table summarizing some of the main food sources used by orioles in summer:
Food Source | Details |
---|---|
Fruits | Raspberries, blackberries, mulberries, cherries, grapes, figs, elderberries |
Nectar | Trumpet vine, foxglove, lilies, columbine, jewelweed |
Insects | Caterpillars, beetles, ants, wasps, spiders |
Nectar | Trumpet vine, foxglove, lilies, columbine, jewelweed |
Do males and females look different in summer?
Male and female orioles can be distinguished by subtle differences in their plumage that become more noticeable in summer.
In most oriole species, the adult male has a vivid black and orange, yellow, or red color pattern. Adult females have a similar pattern but with more olive or greenish hues instead of black. Immature birds resemble adult females.
During the breeding season, the male’s coloration appears richer and darker. The feathers become heavily pigmented due to hormonal changes. This makes the male’s pattern stand out more compared to the paler female.
His striking plumage signals his fitness and helps him stand out on his breeding grounds. It may also aid in mate attraction.
By mid-summer, both male and female orioles undergo a complete molt. Their feathers appear worn and faded until the new ones grow in. Molting may make the genders harder to distinguish.
Do the young orioles look like adults?
Young orioles have a duller, more olive-brown coloration overall with less black than the adults. Their wings also show white wing bars that are not seen in adults.
As they mature, the young gradually take on more adult-like plumage. Males attain their full bright black and orange/red coloring by the following spring. Females acquire more yellowish or olive tones but with less black than males.
So while juvenile orioles may resemble females, they can be identified by their duller hues and white wing bars. By fall, these differences become less obvious.
Baltimore Oriole
The male Baltimore Oriole is a bright orange and black bird. Females are yellow-orange and olive. Juveniles are darker orange-brown with white wing bars.
Bullock’s Oriole
Bullock’s Oriole males are orange and black. Females are yellow and olive-green. Juveniles are darker overall with white wing bars.
Do orioles molt in summer?
Orioles, like most bird species, undergo an annual molt each summer. Their colorful feathers become faded and worn over the course of the breeding season.
The molting cycle allows them to grow a fresh set of feathers before fall migration. Molting takes place from mid-summer through early fall.
Some key facts about oriole molting:
- Males tend to molt earlier than females
- Molting begins as early as June and lasts through August
- Orioles drop feathers gradually over an extended period
- New brighter feathers start emerging while old ones are still present
- Orioles may appear scruffy or patchy during molt
- Molting happens frequently as birds preen and groom
By late summer, both male and female orioles sport a new set of fresh, brightly colored feathers in time for fall migration.
The molting process is metabolically taxing, so orioles tend to eat more during this time to meet energy demands. They may be easier to spot at feeders in mid-summer as their plumage renewal takes place.
When do orioles migrate south?
Most orioles leave their breeding grounds by late summer, apart from some adult males. Southward migration ramps up in August and continues well into September.
Here are some details on the oriole migration timeline:
- Females and immatures start migrating earlier, some as early as late June
- Mass exodus occurs in August through September
- Young birds depart before adults
- Males are the last to leave in the fall
- Peak migration happens late August to early September
- Stragglers may linger into October in the north
Orioles migrating south from the northern U.S. and Canada overwinter in Mexico, Central America, and the Caribbean. Those that breed farther south may only migrate as far as the southern U.S. for winter.
The tropical forests and agricultural areas of Central America provide abundant food during winter when berries and insects are scarce farther north.
Do any orioles stay for winter?
The vast majority of orioles that breed in North America migrate south for winter. But small numbers may overwinter in parts of the southern U.S., mainly Florida and California.
Rare sightings also occasionally occur in other southern states. Wintering orioles are more likely to be male.
Here are a few factors that may allow some orioles to stay north in winter rather than migrating:
- Availability of winter food sources like fruiting trees
- Enough insects and nectar for food in warm climates
- Bird feeders stocked with nectar, fruit, and mealworms
- Adult males better able to withstand cold than females/young
- Less competition for food in the non-breeding season
Overwintering orioles are not always the same individuals each year. Most that stay north do not survive the entire winter.
Notable wintering locations
- Southern Florida
- Coastal California
- Southern Texas
- Louisiana
- South Carolina
Summary – Key facts about orioles in summer
Here are some of the key points covered about oriole behavior in summer:
- Orioles arrive on breeding grounds from March to May depending on location
- Males often return to the same sites; females less so
- Breeding starts shortly after arrival, with peak egg laying in May/June
- Females occasionally raise second broods in summer
- Parents tend to the young for 2-3 weeks after leaving the nest
- Some males stay put all summer, but females and young are more migratory
- Southward migration starts in mid summer, peaks in late August/September
- Orioles eat fruit, nectar, and insects in summer
- Complete molt occurs beginning in early summer
- Plumage differences between males and females get more distinct in summer
- Rare orioles may overwinter in the southern U.S. and south
So while some orioles do remain through the summer, their numbers decrease after breeding season as migrants head south again. But their colorful presence enlivens the summer months while they raise their young.