Tawny owls (Strix aluco) are medium-sized owls found throughout much of Europe and parts of Asia. They are known for their distinctive “too-wit, too-woo” call which can often be heard at night. As with many owl species, there has been some observation and discussion around whether tawny owls ever adopt orphaned chicks or eggs into their nests. Here we will examine the evidence and research around tawny owl adopting behavior.
Do tawny owl parents ever adopt orphaned chicks?
There are a few reported cases of tawny owls potentially adopting orphaned chicks in the wild, however these cases are quite rare. Tawny owls generally only raise their own biological offspring and do not typically accept unrelated chicks into their nests. However, there are occasional exceptions that suggest some flexibility under certain circumstances.
One study conducted in Finland found a case where a pair of tawny owls raised a chick from another nest after its original parents had disappeared. The chick seemed to be accepted and fed by the adopting parents. However, the authors noted this was likely only possible because the chick was still very young and not yet old enough to recognize its parents visually or vocally. So the adopting parents were able to trick the chick into thinking they were its parents. Had the chick been older, it likely would have rejected the imposter parents.
There have been a few other isolated reports of tawny owls potentially adopting an orphaned chick, but most owl experts agree these cases are extremely unusual. Generally tawny owls have strong instinctual bonding behaviors that make adoption of unrelated chicks very difficult except under specific circumstances.
What about adopting orphaned eggs?
There is even less evidence that tawny owls adopt orphaned eggs laid by other birds. One reason is that is more difficult for birds to trick a chick that hatches from an adopted egg, as the chick imprints on the parents it sees immediately after hatching. Additionally, most birds have a strong instinct to only incubate and hatch their own eggs.
Tawny owls usually lay 2-5 eggs per clutch and will not typically lay more than that. So they are unlikely to accept substantially more eggs added to their nest. There are a few cases of some captive owls accepting additional eggs from other birds into their nests. However, adoption of orphaned wild tawny owl eggs by other tawny owl parents remains very rare if it occurs at all. The strong natural instinct is for birds to only care for their own offspring.
Why is adoption rare in tawny owls?
There are several reasons why adoption is uncommon among tawny owls and owls in general:
- Strong natural instinct to only raise their own offspring – Owls have evolved over millions of years to invest energy in passing on only their own genes. Adoption does not offer direct genetic benefits.
- Nest defense – Owls will often aggressively defend their nest site from unrelated birds. This makes leaving an orphaned chick or egg difficult.
- Feeding capacity – Owls can only feed a limited number of chicks based on the food supply near their nest. Adding more mouths to feed stresses the parents.
- Offspring recognition – Chicks imprint on their parents early on. Foreign chicks will often not be accepted.
- Egg rejection – Bird eggs have unique patterning making foreign eggs in a nest more obvious. Owls tend to reject eggs not their own.
Because of these reasons, adoption essentially goes against tawny owls’ core instincts shaped by natural selection. Cases where it may occur require very specific circumstances and are likely very rare events.
Have any owl species been observed adopting more frequently?
Most owls have a strong natural resistance towards adopting unrelated chicks or eggs. However, there are a couple owl species that do exhibit somewhat higher rates of adoption compared to others:
Barn Owls
Barn owls are one species where adoption has been observed more frequently in the wild. Researchers have documented numerous cases of barn owls caring for chicks not biologically their own. One study in Spain found over 7% of barn owl nests contained at least one adopted chick.
Some reasons why barn owls may be more likely to adopt include:
- Larger average clutch size – Barn owl clutches often contain up to 10 eggs, increasing capacity.
- Higher nest site competition – Barn owls have limited nesting cavities, leading to more squatting.
- Looser pair bonds – Barn owls switch mates between seasons more readily.
Overall barn owls seem to exhibit a slightly more flexible adoption strategy compared to more solitary and territorial owl species. But adoption still remains uncommon relative to raising their own offspring.
Great Horned Owls
Great horned owls have also exhibited some rare cases of adoption in the wild. Their larger size and ferocity makes them more likely to take over an existing nest if their own fails. There are some documented cases of great horned owls adding an orphaned chick into a nest with their own chicks. Their larger brood size of up to 5 chicks provides some capacity for an extra.
Additionally, great horned owls sometimes utilize old hawk or heron nests, making squatting and potential adoption more feasible. Overall however, adoption is still considered extremely rare in great horned owls. Their strong natural instincts generally prohibit incorporating unrelated offspring.
Can adoption be encouraged in captivity?
There have been some cases where avian rehabilitators and captive breeding programs have been able to intentionally encourage owl adoptions:
Hand-rearing chicks
If a chick is hand-raised by a caretaker from a very early age, it can potentially be introduced and accepted into a captive owl nest. The parents may see the chick as their own since it was put in their nest before its eyes opened. However, this is still not always successful as owls recognize genetic relatedness.
Placing eggs first
Similarly, placing an orphaned egg in the nest of a captive pair prior to their own eggs being laid can increase chances of adoption. The owls often will simply start incubating whatever eggs appear first. However again, the hatchlings are sometimes rejected.
Removing eggs
Temporarily removing the parent’s own eggs has shown some success in forcing the pair to accept orphaned chicks placed into the empty nest. But the original eggs must be removed carefully and replaced shortly after. This essentially tricks the parents into starting the bonding process with the orphaned chicks before their own hatch.
Nest boxes
Providing nest boxes for captive owls can create higher site competition and potentially increase willingness to adopt extra eggs or chicks. In the wild, most owls are highly territorial about actual nest sites. But boxes reduce this territorial behavior.
So while natural owl adoption may be extremely rare, some techniques can induce adoption in captive or hand-reared scenarios. However the owls’ instincts are still fundamentally tuned towards only raising direct genetic offspring. Adoption goes against millennia of inherited behavioral patterns in these birds.
Conclusion
In summary, most evidence indicates that wild tawny owls essentially never intentionally adopt orphaned chicks or eggs on their own. Their instincts have evolved to direct all their parental resources towards their own biological young. However, there are occasional rare cases where they may accept an orphaned chick due to unusual circumstances. And other owl species like barn owls or great horned owls exhibit slightly higher, but still very minimal, occurrences of natural adoption in the wild. These rare cases provide an interesting glimpse into the flexibility that exists within owl parental behaviors. But largely, owls appear pre-programmed by evolution to avoid adoption and instead only raise offspring carrying their own genes. With human intervention, some adoption can be induced for rehabilitation or captive breeding purposes. But adoption overall remains an extremely unusual phenomenon in nearly all owl species. Their evolutionary strategy is centered on dedication to their own direct offspring.