Swallows are small passerine birds that are found worldwide. There are around 90 different species of swallows, including the barn swallow, tree swallow, and cliff swallow. Swallows build nests out of mud or saliva, which they use for breeding and raising their young. An interesting question that often comes up is whether swallows use the same nest more than once, or if they build a new nest each year. In this article, we will examine the evidence and research on swallow nest reuse.
Do swallows reuse nests?
The short answer is yes, swallows often do reuse nests, but there are some caveats. Studies have found that cliff swallows and barn swallows frequently use the same nests across breeding seasons. However, reuse rates vary across species, locations, and individual nests. Nest reuse may depend on nest durability, nest site availability, and past breeding success.
For example, one study by Brown and Brown (1996) found that cliff swallows in Nebraska reused nests 35% of the time. The most durable nests had reuse rates of up to 70%. However, other colonies had much lower reuse rates of 6-12%. Barn swallows have been found to reuse nests 51% of the time in Ontario, Canada (Shields 1984). Tree swallows also reuse nest boxes, but at lower rates of around 11-33% (Winkler et al 2005).
Reuse is likely common because building a new nest each year requires a lot of energy. Swallows can conserve resources by reusing an existing, undamaged nest. However, they may build new nests if the old ones became too degraded or infested with parasites. The presence of old nests may also help attract swallows to reuse the same colony site year after year.
Why do swallows reuse nests?
There are several key reasons why swallows frequently reuse nests:
Saves energy and resources
Building a nest from scratch is expensive for swallows in terms of time, energy, and resources. Constructing a new mud nest requires over 1000 trips to gather wet mud and straw. By reusing an intact nest from the previous year, swallows save themselves a lot of effort. This gives them more time and energy to devote to other important activities like finding food and mating.
Quickly establish breeding sites
Reusing a nest allows swallows to start breeding earlier in the season. Swallows are migratory birds that return to the same nesting sites each spring. Arriving birds can start egg-laying almost immediately if old nests are available. In contrast, swallows nesting in new, unfinished sites may experience delays which reduce breeding success.
Nest durability
Many swallow nests are quite sturdy and withstand weathering from multiple seasons. Mud nests baked hard in the sun can often persist for many years if undamaged. The structural integrity of the nest may be a key factor determining the likelihood of reuse. More durable nest structures have higher reuse rates.
Familiarity with site
By reusing the same nest over multiple years, swallows maintain site familiarity. Returning to a known nest may provide information about the suitability of the breeding habitat. Past nesting success and predation rates influence whether sites are reused.
Social attraction
In colonial species like cliff swallows, the presence of old nests helps attract birds to a site. Early arrivals may be drawn to reuse sites by the presence of intact nests from previous years. This helps facilitate colony formation.
Limited nest site availability
Good nesting sites may be limited, especially for cliff and bank swallows that nest on vertical surfaces. Suitable mud nesting sites are rare in some habitats. Reusing a durable nest may be preferable to building a lower-quality nest in a marginal site. Reuse is higher when nest sites are limited.
Benefits of nest lint
Lint and debris accumulate in nests over time. Researchers think old nest lint may help regulate nest climate, limit parasite infestations, or camouflage the nest. Lint reuse could provide benefits that increase reuse rates.
How long do swallow nests last?
The durability and lifespan of mud swallow nests depends on factors like weather, construction, and nest position, but many can persist for years. Here are some estimates for nest longevity:
– Cliff swallow nests may last 1-6 years, with an average of 3 years. Those protected from rain and damage can last up to 15 years.
– Barn swallow nests typically last 1-3 years. With suitable protection, they may persist for up to 7 years.
– Tree swallow nest boxes can be usable for 2-10 years if maintained.
– Bank swallow nest burrows usually only last 1 year before collapsing, since they are dug into soft soil cliffs.
Heavy rainfall, severe storms, or nest predators can all decrease nest lifespans. Position also matters – exposed outer nests degrade faster than more protected interior ones. Careful nest construction using thick layers of mud helps strengthen and prolong nest durability. Swallows may build a nest dome or tunnel to increase protection.
Do swallows perform nest maintenance?
Yes, swallows engage in nest repair and maintenance both within and between seasons. This helps prolong the usable life of a nest.
Swallows may repair their nests even during the breeding season to fix damage or reinforce the structure. One study found cliff swallows spent over 2 hours per day maintaining their nests while actively nesting (Brown and Brown 1996). Pairs may take turns gathering mud to patch holes, rebuild fallen sections, or reinforce the nest rim after heavy rains.
Between seasons, leftover nests often require refurbishment before they can be reused. Upon returning in spring, swallows may rebuild damaged sections, add a fresh mud layer, or line the interior with new soft feathers. One study found barn swallows spent 1-4 days sprucing up old nests for reuse (Shields 1984). Efforts focus on restoring structural integrity and insulation.
This habitual nest upkeep by swallows is likely crucial for maintaining durable nests that can withstand multiple years of use. It demonstrates nest reuse provides major benefits that make the extra effort worthwhile.
Do any other bird species reuse nests?
Many other bird species, both passerines and non-passerines, reuse nests. Here are some examples:
– Ospreys rebuild and reuse large stick nests for up to 30 years.
– Bald eagles repair and reuse nests for 5-10 years on average.
– Some ducks and geese reuse nest sites or even relic nests from previous years.
– Small passerines like robins, phoebes, and bluebirds may reuse nests or nest boxes.
– Woodpeckers reuse cavities they’ve carved for multiple broods or years.
– Burrowing owls reuse abandoned mammal burrows.
– Cornell nest boxes maintained for research have been used by birds for over two decades.
As with swallows, nest reuse is likely an adaptive behavior to conserve energy and resources across breeding attempts. Prior experience with a successful nest site is also beneficial. Cavity nesters in particular are dependent on suitable natural or excavated holes, favoring reuse.
Why don’t swallows always reuse nests?
While nest reuse is common in swallows, they do not reuse nests 100% of the time. Here are some reasons why swallows may abandon or build new nests:
Nest structural failure
If the old nest has become severely degraded, collapsed, or been damaged from weather, predators, or parasites, it may be unsalvageable. Swallows must start fresh if the nest foundation cannot be repaired.
Nest infestations
Reusing an old nest comes with risks like carry-over parasite loads. To avoid mites and other nest infestations, swallows may construct new uncontaminated nests.
Predation
Heavy predation may make sites with reused nests more conspicuous to predators. Nearby new sites may be less risky.
Habitat changes
Significant local habitat alterations like vegetation loss or reduced food availability can make a former site unsuitable. Swallows may be forced to establish new nest sites.
Mate switching
If swallows get new mates, they may build fresh nests together. Mated pairs are more likely to reuse nests.
Multiple brooding
Swallows attempting second broods often build new nests nearby to allow simultaneous brooding in old and new nests.
Colony dynamics
For colonial swallows, changes in group size or competition may favor new nests. Nests in prime locations are more likely to be reused.
So while nest reuse is beneficial, swallows balance these benefits with the needs of their dynamic breeding ecology. Their adaptability allows them to assess each situation and build new or reuse nests as optimal.
How do young swallows acquire nests?
Young swallows returning to their colony for the first time cannot reuse their own natal nests. So how do swallow fledglings obtain nests?
Nest prospecting
Even before fledging, young swallows explore and investigate potential nesting sites around their colony. This helps them locate usable old nests. They may return to prospected sites the next year.
Social attraction
Unmated swallows are attracted to join breeding colonies with lots of old nests. This allows new pairs to claim abandoned nests.
Nest competition
Established pairs may drive competitors away from prime reused nests. Displaced swallows are forced to nest in suboptimal or new spots.
Nest building
Young swallows new to a colony often still have to construct new nests from scratch, usually in less ideal locations. But this allows them to eventually reuse these nests in following years.
Nest takeovers
Swallows may directly take over a reused nest by driving away or replacing the previous owners.
Inheritance
Offspring may inherit their parents’ nest after a breeding season if the nest remains usable.
Through some combination of nest prospecting, competition, construction, and inheritance, young swallows work to establish ownership over nests suitable for reuse over multiple years. It takes time, effort, and experience for swallows to secure consistent nest sites and maximize reuse.
Do swallows have nest site fidelity?
Yes, swallows show strong nest site fidelity. They display a clear tendency to return to the same nesting colonies year after year.
For example, studies of cliff swallows marked with leg bands found that the vast majority returned to their original colony site in future breeding seasons, even when other sites were available (Brown and Brown 1996).
Barn swallows also demonstrate high nest site fidelity. A Swiss study found that 78% of banded barn swallows returned to their previous nesting building, and 92% came back to use the same general nesting area (Schaub et al. 2012).
Nest site fidelity provides swallows with multiple potential benefits:
– Reusing familiar nest sites saves time and energy
– Returning to successful sites with good nests increases reproductive success
– Renewing social bonds with previous colony mates
– Maintaining site claim against competitors
– Habit and evolutionary preference for philopatry
However, adverse conditions like nest destruction, parasite infestations, or dramatical habitat change can cause site abandonment. So while swallows generally prefer fidelity, they can adapt to new nesting locales as needed.
Overall, the tendency of swallows to reuse nests and return to previous colony sites across breeding seasons appears to improve breeding outcomes. Nest reuse and site fidelity represent adaptive behaviors evolved to maximize swallow reproductive success.
Conclusion
In summary, research evidence clearly shows that swallows frequently reuse old nests for subsequent breeding attempts rather than building new nests each year. All swallow species demonstrate some rates of nest reuse, but Barn Swallows and Cliff Swallows are most associated with this behavior.
Swallows reuse nests to save energy, quickly start breeding, leverage nest durability, maintain site familiarity, facilitate colony formation, and benefit from nest lint. However, they may still construct new nests if old ones fail structurally, become infested, or the site becomes unsuitable. Most swallow nests can persist for a few years up to over a decade with periodic maintenance.
Beyond reusing nests, swallows also exhibit nest site fidelity by returning to previous colony locations. This philopatric behavior likely coevolved with nest reuse to maximize habitat familiarity and breeding success. While not obligatory, nest reuse and site fidelity are ingrained behaviors in swallow life history strategies. Careful nest construction and maintenance supports repeated nest use, highlighting the adaptive benefits. Understanding swallow nesting behavior provides fascinating insight into avian ecology and evolution.