Cardinals are a familiar red bird that can be found across much of North America. One interesting behavior that can be observed in cardinal flocks is that of birds feeding one another. This seemingly altruistic act raises questions about why cardinals engage in this behavior. Here we will explore the reasons why cardinals feed each other and the benefits it provides them.
Why Do Birds Feed Each Other?
There are several reasons why cardinals and other bird species engage in allofeeding, or the act of feeding other adult birds.
Feeding Their Mates
One of the most common reasons is that birds will feed their mates. Cardinals form monogamous pair bonds that can last for many years. The male and female cardinal work together to build nests, raise young, and defend their territory.
Feeding their mate helps strengthen the pair bond. It may also serve as a part of mating behavior, with the male offering the female food as a courtship display. This feeding reinforces the social bond between the mated pair.
Feeding Their Young
In addition to feeding their mates, parent cardinals also provide food for their chicks. Cardinal parents are dedicated providers that both gather food and deliver it back to nestlings.
The chicks beg and call loudly when hungry. Both the male and female cardinal hurry back and forth to the nest with beakfuls of insects, seeds, and berries to feed the demanding youngsters. This parental feeding is crucial for the growth and survival of cardinal fledglings.
Feeding Other Family Members
Cardinals may also feed other related birds within their family group or flock. Groups of cardinals often include offspring from previous nests that remain with their parents for multiple seasons.
These related birds will sometimes continue to beg for food from their parents or older siblings. This helps maintain social bonds within cardinal families.
Sharing Abundant Food Resources
When cardinals find an abundant source of food, they may gather in larger flock sizes. One bird that locates a feeder or fruiting bush will sometimes call to flockmates.
These gatherings around plentiful resources result in increased allofeeding between flock members. Dominant birds may allow subordinates to feed alongside them. The increased food availability means feeding other birds comes at a lower cost to the donor bird.
Maintaining Social Hierarchy
Dominant cardinals may feed subordinate birds to maintain the social order of the flock. By feeding lower ranking birds, dominant individuals reinforce their higher position.
This helps minimize conflict and reinforce relationships between cardinals of differing status. Allowing subordinates to feed ensures they remain a cohesive flock.
Ill and Injured Birds
Sick or injured cardinals sometimes receive allofeeding from flockmates. This helps keep ill and weakened birds alive during times of injury or recovery.
Cardinals have been observed feeding nestmates that were injured and could not gather food themselves. This may demonstrate altruism or empathy in cardinals towards sick or impaired flockmates.
What Are the Benefits of Feeding Others?
The act of allofeeding provides a range of benefits for both the donor and receiver bird. These mutual benefits help explain why the behavior continues to occur in cardinal flocks.
Benefits for the Donor Bird
The donor bird who provides food to another gains several advantages:
- Strengthens pair bonds with mates
- Teaches young how to feed themselves in the future
- Helps family members survive and reproduce their shared genes
- Gains social status and minimizes conflict
- Demonstrates resource holding power at abundant food sources
Overall, altruistically feeding other birds can reinforce social bonds, demonstrate dominance, ensure reproduction, and promote family genes into the next generation.
Benefits for the Receiving Bird
The birds receiving the donated food also gain significant benefits:
- Provides supplemental food and nutrients
- Improves chances of survival and future reproduction
- Saves energy from constantly searching for food
- Allows sick/injured birds a chance to recover
- Food given to chicks supports growth into adulthood
For birds that receive allofeeding, the additional food resources help them survive periods of hardship and give them greater fitness. This is especially crucial for vulnerable chicks and injured birds.
How Do Cardinals Feed Each Other?
Cardinals have specialized beak and digestion adaptations that allow them to effectively transfer food from one bird to another. Here is an overview of how cardinal allofeeding works:
Regurgitation
The most common method cardinals use to feed other birds is regurgitation. The donor bird will swallow food into its crop, a pouch-like enlargement of the esophagus.
The bird then regurgitates this food back up its throat and uses its beak to transfer the regurgitated food into the mouth of the receiving bird. Cardinals have wide, deep beaks well-suited for transporting regurgitated food.
Beak-to-Beak Transfer
Another direct method is for the cardinal to carry food in its beak, then transfer it directly into the mouth of the recipient. The donor bird grasps food in its beak and presents it to the receiving bird, which takes it directly from the provider’s beak.
Dropping Food
Sometimes a cardinal will simply drop or place food it was carrying, allowing another bird to pick it up and consume it. This may happen near nests, allowing the sitting mate to receive the food. It also occurs at abundant food bonanzas, where dominant birds drop excess food they cannot eat.
Feeding Young
Cardinal parents use regurgitation and beak-to-beak transfer to deliver food to nestlings. The chicks gape wide and beg loudly, stimulating the parent to regurgitate food directly into their gaping mouths. This efficient process ensures the young get adequate nutrition.
Billing
Billing is a gentle behavior in which a mated pair of cardinals clasp their beaks together. They may simultaneously rub their beaks along one another’s. This affectionate gesture helps strengthen pair bonding.
What Foods Do Cardinals Feed Each Other?
Cardinals are omnivorous birds that feed on a diverse range of plant and animal material. Here are some of the main food items cardinals may transfer when allofeeding:
Seeds and Grains
Cardinals often feed each other seeds from grasses, fruiting plants, and agricultural grains like corn and oats. These small, hard seeds are swallowed easily, stored in the crop, and then regurgitated to transfer to another bird.
Fruit
Fruits like berries are another frequent component of the cardinal diet. They deliver essential nutrients and sugars. Cardinals pluck ripe berries and can regurgitate pulp and juice to share fruit meals with flockmates.
Insects
Protein-rich insects and other invertebrates are fed extensively to nestlings and supplements the diet of adults. Cardinals capture caterpillars, beetles, ants, grubs and other insects to transfer to mates and offspring.
Nuts
Various nuts and seeds like sunflower seeds are common at bird feeders. Cardinals may fill up on these and redistribute them to other flock members through regurgitation or dropping them.
Suet
Rendered fat from beef or mutton is provided by humans in suet feeders. Cardinals scrape off and eat bits of suet, then may transfer chunks to their young or mates.
Food Item | Description |
---|---|
Seeds and Grains | Small seeds from grasses and agricultural crops |
Fruit | Berries and pulp from trees and bushes |
Insects | Protein-rich insects and invertebrates |
Nuts | Sunflower seeds, nut pieces from feeders |
Suet | Rendered fat from animal meat |
How Often Do Cardinals Feed Each Other?
The frequency of allofeeding in cardinals depends on a few factors:
Time of Year
Allofeeding increases during the breeding season as mated pairs strengthen bonds and feed young. It is extremely common during spring and summer when nestlings are present.
Frequency drops in fall and winter when cardinals do not nest and often feed in smaller, less cooperative flocks.
Food Availability
When food is scarce due to weather or habitat changes, cardinals are less likely to share meals. But at abundant, clumped food sources, allofeeding becomes more common as cardinals share extra food.
Social Factors
In hierarchical flocks with family groups, allofeeding is more frequent as a way to reinforce status and bonds. Pairs and family members feed more often. In looser winter flocks, there is less social pressure to share food.
Condition of Recipient
Ill or injured birds elicit more allofeeding as they cannot feed themselves easily. Chicks also stimulate extremely high rates of allofeeding from their parents.
Overall, the frequency ranges from hundreds of daily feedings for chicks to occasional allofeeding in non-breeding flocks. The average cardinal participates in allofeeding on a regular basis.
Do Other Bird Species Exhibit Allofeeding?
Many other bird species beyond cardinals exhibit allofeeding behaviors:
Doves and Pigeons
Pigeons and doves are prolific allofeeders. They produce nutrient-rich “crop milk” to feed nestlings, provide courtship feeding of mates, and feed juveniles and subordinates.
Parrots
Parrots mate for life and demonstrate extensive allofeeding, especially during breeding. They provision mates at the nest cavity and may hand-feed special foods.
Titmouse
Chickadees, titmice, and other songbirds feed mates, young, and sometimes unrelated flockmates. This social feeding cements flock bonds.
Corvids
Ravens, crows, and jays allofeed mates and offspring. Young from previous years may also remain with family groups and receive occasional feedings.
Finches
Gouldian finches court prospective mates via ritualized allofeeding. The male feeds the female packed seeds to demonstrate his parental abilities.
Hummingbirds
Male hummingbirds feed females as part of their elaborate breeding rituals. Providing nectar demonstrates the male’s fitness and resources.
Bird Group | Allofeeding Behaviors |
---|---|
Doves and Pigeons | Crop milk for young, courtship feeding |
Parrots | Feeding at nest, special courtship foods |
Songbirds | Feeding mates and flockmates |
Corvids | Feeding family members and juveniles |
Finches | Courtship feeding displays from males |
Hummingbirds | Nectar feeding during courtship |
What Are Some Theories on the Evolution of Allofeeding?
Evolutionary biologists have proposed several theories for how allofeeding behaviors may have evolved in birds:
Kin Selection
Kin selection posits that birds feed relatives to promote the passage of shared genes into the next generation. By assisting kin, birds indirectly help propagate copies of their own genes.
Reciprocal Altruism
This suggests birds allofeed to gain future reciprocation of the behavior. Feeding others creates a social “debt” that birds repay later on.
Prestige-Based Model
According to this model, public allofeeding signals a bird’s quality as a mate or social partner. It evolved as a costly display of fitness.
Food Sharing Model
This proposes allofeeding allows birds to redistribute food efficiently in variable habitats. It functions to maximize use of ephemeral food sources.
Social Cohesion Model
By this theory, allofeeding enhances social bonds essential for group-living birds. It helps maintain vital flock cohesion and hierarchies.
While the evolutionary roots remain debated, allofeeding clearly enhances cardinal reproduction, survival, and sociality today.
Conclusion
Allofeeding is a common and important behavior seen in cardinal flocks and many other bird species. Cardinals may feed others to nourish mates, chicks, and family members. This social feeding strengthens bonds, teaches young, and supports struggling birds.
Through regurgitation, birds can efficiently redistribute essential foods like fruit, seeds, and insects. Allofeeding provides nutrition and also seems to signify social status, demonstrate mating fitness, and encourage group cohesion. Further research can continue unveiling both its function and evolutionary origins.
Regardless of its roots, watching a cardinal delicately feed a mate or recent fledgling offers a glimpse into the family ties and complex interactions of these familiar red birds. The cardinal’s melodic song and flashy plumage may catch our eye first, but looking closer reveals an intricate social world structured around the reciprocal exchange of food.