Horned puffins are seabirds that belong to the auk family. They are found in the northern Pacific Ocean and spend most of their lives out at sea, only coming to land during breeding season. Horned puffins are highly social birds that live and breed in large colonies during the summer months. However, there has been some debate among ornithologists about whether horned puffins continue to associate in groups during the nonbreeding season when they are out at sea. In this article, we will examine the evidence and research around group living in horned puffins outside of the breeding colonies.
Breeding Colony Behavior
There is no question that horned puffins form large, dense breeding colonies during the summer months when they come ashore to nest. They choose steep, grassy cliffs along the coast to dig their nesting burrows where they raise their young. A single breeding colony may contain thousands of pairs of horned puffins. The birds are highly social during this time, interacting frequently through vocalizations, displays, and physical contact. This group breeding behavior likely provides protection from predators, easier exchange of information, and other collective benefits.
| Location | Estimated Colony Size |
|---|---|
| Semidi Islands, Alaska | 250,000 pairs |
| St. George Island, Alaska | 50,000-100,000 pairs |
| Cape Pierce, Alaska | 47,000 pairs |
Some of the largest known colonies of nesting horned puffins contain tens or even hundreds of thousands of breeding pairs each summer. The implications of these huge aggregations are that the species is highly social and benefits from colonial living during the breeding season.
Post-Breeding Dispersal
Once the summer breeding season is over, horned puffins leave their colonies and head out to sea. This mass dispersal occurs in late summer and early fall as the birds leave en masse and migrate south to spend the winter months floating on the open ocean. Tracking studies using geolocators attached to horned puffins show that the birds move away from their breeding colonies in Alaska and British Columbia and spread out over a large area in the northern Pacific Ocean off the coasts of Alaska, Canada, and Russia.
Their distribution during this post-breeding dispersal and migration seems to be shaped mainly by optimal food resources. Horned puffins feed on small fish, marine invertebrates, and zooplankton. They are found in parts of the ocean during the winter where their prey is abundant at depths they can dive and reach. Unlike their dense aggregations on land during breeding season, horned puffins are much more dispersed and spread out once they are at sea.
Behavior and Interactions at Sea
When floating on the open ocean in the winter months, horned puffins are most often observed alone or in pairs, probably consisting of mated pairs that stay together. Small flocks of up to a dozen birds are sometimes seen, but large aggregations are uncommon. This suggests that they do not form large cohesive social groups while at sea.
However, a few interesting behavioral observations provide clues that horned puffins may still interact and associate with conspecifics in loose, open groups during the nonbreeding season:
- Roosting groups – Horned puffins have been observed roosting in loose groups along drift lines of floating seaweed.
- Foraging flocks – Small flocks will sometimes converge and feed together where prey is abundant.
- Posture mimicking – When one horned puffin dives under the water, others nearby often follow and mimic the behavior suggesting some social information sharing.
Additionally, horned puffins have been seen associating in mixed flocks with other auk species while floating at sea in winter. These include thick-billed murres, parakeet auklets, and tufted puffins. Associating with other seabirds may provide some collective anti-predator advantages.
So while they do not form dense colonies as they do during breeding season, there are some indications that horned puffins may still prefer some degree of loose social grouping and behavioral synchrony when at sea and interacting with conspecifics. This is likely driven by shared requirements for food, protection, and habitat rather than obligate colonial nesting.
Habitat Factors
In addition to direct social behavior, there are some habitat factors that may bring horned puffins in greater proximity and promote group associations during the nonbreeding season:
- Wintering areas – Horned puffins winter in concentrated regions of the Bering Sea, Sea of Okhotsk, and Sea of Japan where prey is seasonally abundant. This clumped distribution may lead to higher densities.
- Foraging hotspots – Certains islands, shoals, shelf breaks, and hydrographic features concentrate prey, attracting and concentrating foraging horned puffins.
- Predator avoidance – Rafting together near drift lines and islands may provide protection from aerial predators.
So while horned puffins are not obligatorily colonial when away from breeding sites, aspects of their winter ecology and habitat use may result in open groupings, flocks, and higher local densities in certain areas. This reflects a more flexible social structure in the nonbreeding season compared to obligate colonial breeding.
Changes Outside of Breeding Season
To summarize the key changes in horned puffin social behavior outside of breeding season:
- Colony size declines from thousands to ten or fewer individuals.
- The location shifts from dense colonies on cliffsides to dispersed offshore waters.
- Interactions are reduced but some synchronized diving, flocking, and rafting occurs.
- Habitat features lead to loose aggregations in some areas.
So horned puffins transition from highly colonial and aggregated breeding groups to being more solitary or loosely gregarious when at sea. But they still associate in open groups and flocks at times, especially when resources are clumped. Their social flexibility allows them to shift strategies as conditions change.
Conclusion
In conclusion, the evidence suggests that horned puffins do continue to live in loose groups and open aggregations during the nonbreeding season, even if they are not as tightly clustered as in their breeding colonies. Their social flexibility allows them to transition between dense breeding colonies in summer and looser floating flocks in winter. This mix of solitary and group behaviors depending on context enables horned puffins to thrive in both their breeding areas and marine habitats. Their seasonal shifts in social behavior are a strategy adapted to the habitats and resources critical to their life cycle.
