Small birds following larger predator birds like hawks is a phenomenon that has been observed by many bird watchers over the years. This seemingly strange behavior raises some interesting questions about why small songbirds would follow a bird that is known to prey on them. In this article, we will explore some of the main theories behind this behavior and look at the evidence for and against the idea that small birds actively follow hawks.
Do small birds really follow hawks?
There is quite a bit of anecdotal evidence from birders that smaller songbirds like chickadees, nuthatches, titmice, and warblers can often be seen near or following after hawks. This includes sharp-shinned hawks, Cooper’s hawks, and even large hawks like red-tailed hawks. The small birds usually keep a safe distance from the hawk but seem to be attracted to it or following it deliberately as it moves through the forest. This has been noted by seasoned birders time and time again in the field.
There have also been some more systematic observations and studies that confirm this tendency of small birds to associate with hawks. For example, researchers in Maine found that flocks of small birds moved in proximity to northern goshawks more often than would be expected by chance. Another study in Alberta, Canada found that winter flocks of black-capped chickadees associated more with sharp-shinned hawks than merlins, another small falcon. There is evidence that some species even change their calls when a hawk is nearby.
Overall, the many anecdotal reports combined with some scientific observations suggest that there is a real phenomenon where smaller songbirds are attracted to hawks or intentionally follow them at least part of the time. But this raises the obvious question – why would they do this when hawks eat small birds?
Theories on why small birds follow hawks
There are a few main theories proposed by researchers on why small birds seem to be interested in hawks and sometimes follow them closely:
- Mobbing – Small birds may harass or mob the larger predator to drive it away from their territory or nests by dive bombing it. This is likely part of their anti-predator defense.
- Early warning system – By keeping tabs on the hawk, the small birds can warn each other quickly when the hawk is on the hunt. This gives them time to hide or flee.
- Food source – Small birds may follow hawks hoping to steal food scraps or prey remains after the hawk has eaten.
- Protection – Being near a hawk may reduce the chances of being attacked by other predators like cats or other hawk species.
There is some research evidence to support each of these theories, though none can fully explain the phenomenon. Let’s look at the evidence for each idea.
Mobbing behavior
Mobbing refers to when prey animals team up to aggressively dive bomb, call at, or harass a predator to drive it away. This is considered an anti-predator behavior and has been observed in many bird species. When a hawk enters the territory of smaller birds, they may mob it in an attempt to protect their nests or young. Some research has found increased mobbing behavior when hawks were present, supporting the idea that mobbing explains some following behavior.
Early warning system
By keeping an eye on where the hawk is and what it is doing, small birds can warn each other about imminent danger through alarm calls. Studies have found that chickadees and other species make more mobbing calls in the presence of hunting raptors. Having this early warning could allow small birds to quickly take cover or flee from an attacking hawk. Their survival depends on quick reactions to threats.
Gaining food source
Hawks are messy eaters and often leave scraps of prey scattered around after making a kill. By following a hawk, small birds may gain access to these remains and leftover bits of food. This supplemental food source could be beneficial and the reason some small birds stay near hawks after they have eaten. However, there is little evidence that small songbirds actually eat the hawk’s leftovers regularly.
Predator protection
One somewhat counterintuitive idea is that small birds may follow hawks for protection. Being near a hawk likely means other predators like house cats are less likely to attack the small birds. Some experiments using fake predator models provide limited evidence for this theory. But overall there is not strong evidence that proximity to hawks reduces attacks by other predators.
Do hawk followers gain benefits?
The fact that small birds so often follow hawks suggests they must be gaining some advantage from the behavior, even if each theory has flaws. Researchers have tried to directly study the costs and benefits of following hawks to look for insights.
One study in Canada tested the early warning system idea by looking at differences in hawk following behavior between adult and juvenile chickadees. They found that adult birds followed accipiters (small hawks) more closely and were quicker to issue alarm calls. Juveniles did not follow as closely. This supports the idea that following is an important anti-predator tactic.
Other research in Maine tested whether chickadees in flocks that associated with northern goshawks had higher overwinter survival rates. They found no difference in survival between flocks that followed goshawks and those that did not. But this study was limited to winter months and did not completely rule out potential benefits.
Overall there is still no smoking gun evidence that following hawks boosts survival or provides a major advantage. But the behavior is so widespread in songbirds that scientists believe there must be some adaptive benefit, even if it is hard to quantify in field studies.
Do all small bird species follow hawks?
While many songbirds have been observed near hawks, some small bird species seem to follow raptors more than others. In particular, chickadees, titmice, nuthatches, and warblers are most frequently reported as hawk followers.
Species that flock together in winter like chickadees may benefit most from coordinated mobbing or gaining early warning when hawks approach. Birds with good eyesight like chickadees may also find it easier to keep an eye on the hawk from a safe distance.
In contrast, species that are solitary and territorial during the breeding season, like some warblers, are not expected to follow hawks as often. Birds with certain physical traits may follow more as well. For example, one study found birds with short wings that make quick flourishes stayed closer to hawks than weaker fliers.
In general, the ability and tendency to follow hawks seems to depend on a species’ social structure, habitat, anti-predator adaptations, and other factors.
Do hawks notice or care that small birds follow them?
Given how stealthy hawks are when hunting, it may seem surprising they would tolerate small birds mobbing them or following their movements. Do hawks notice these small birds at all? And if they do notice, does it impact them in any way?
Research suggests that hawks definitely notice the mobs of small birds nearby. One study tested this directly by measuring changes in head movements in hawks when flocks of small birds were present. The hawks moved their heads more frequently when the small birds were vocalizing and mobbing them. This indicates the hawks visually track the birds harassing them and see them as a threat.
Being constantly harassed and mobbed may make it harder for a hawk to successfully hunt. One study played recordings of small bird alarm calls and found it made captive hawks less likely to approach food. This suggests the mobbing has a real effect on the predator. However, hawks may also learn to ignore small birds over time as they gain experience hunting.
Overall, evidence shows hawks are aware of the small birds, though mobbing may only have minor impacts on their success rate. The dynamic between hawk and songbird is certainly complex on both sides.
Conclusion
Small birds following hawks is a fascinating predator-prey interaction. The phenomenon is certainly real, as confirmed by numerous observations over decades. Small birds likely gain some anti-predator advantages by keeping tabs on raptors and mobbing them, including early warning and predator deterrence. However, the exact benefits to different songbird species are still being researched. Hawks notice the harassment from small birds, though they appear able to tolerate it with minimal impacts on their hunting ability. Understanding the intricacies of these interspecies relationships remains an active area of research.