Birds have a unique way of dealing with their baby’s poop. Unlike mammals that allow their young to poop wherever, parent birds will catch their baby’s feces in a mucus-like membrane called a fecal sac. The adult birds then dispose of these fecal sacs to keep the nest clean. This behavior is common in songbirds and other altricial species where the chicks are born helpless. The fecal sacs allow the parents to maintain sanitary conditions in the nest which is important for the chicks’ health. But what exactly do parent birds do with the fecal sacs once they have collected them? There are a few common practices.
Carry Them Away from the Nest
One of the most frequent things parent birds will do with fecal sacs is carry them away from the nest and drop them far away. This is an efficient way to keep the nest area clean and reduce the chances of attracting predators. The adult birds will transport the fecal sacs in their beak or claws and then drop them at a distance from the nest. Sometimes they may wipe or scrape their beak on a branch afterward to remove any residue.
The parents want to ensure the fecal sacs are disposed of properly and will often select an intentional dropping area. Fecal sacs are commonly found collected under specific trees, on fence posts, or other regular spots. The birds essentially create a toilet area for their young. Carrying the fecal sacs away from the nest right away means less mess and smell around the vulnerable chicks.
How Far Do They Carry Them?
Studies have looked at how far away parent birds will discard their chicks’ fecal sacs. One study of pearly-eyed thrashers in Puerto Rico found the adults dropped the fecal sacs anywhere from 2 to 146 meters away from the nest. On average though, they carried them around 37 meters away.
Another study of woodland flycatchers in Michigan found similar results. The average distance the fecal sacs were dropped from the nest was 38.7 meters. The further the adult birds can transport the waste, the better for keeping predators away. This behavior also reduces the chances of parasites and infections in the nest.
Consume Them
While many birds discard their chicks’ fecal sacs far from the nest, some species will actually consume them. The waste contains nutrients from the food the parents provided earlier. So, eating the fecal sac recoups some of these lost nutrients. This is more common among bird species that can’t afford to lose resources.
Consuming the waste may also help hide evidence of the nest from predators. If the birds eat the fecal sacs, there is less accumulation of waste nearby to signal a nest is in the area. Some theories suggest the chicks’ feces may provide beneficial probiotics to the adults as well. Overall, eating the waste allows the diligent parents to keep the nest clean and nourished.
Which Birds Consume Fecal Sacs?
Some bird groups known to consume their chicks’ fecal sacs include:
- Seabirds like penguins and albatrosses. These birds nest in open areas with little cover so eating waste helps conceal the nest.
- Raptors including eagles, hawks, and owls. Many nest on cliffs or other exposed sites.
- Wading birds like herons. Nesting over water means few places to discard waste.
- Small songbirds. They have high metabolisms and can use the nutrients.
Scientists have recorded over 100 species across numerous bird families that eat their young’s fecal sacs. The behavior is more frequent when food is scarce or harder to find.
Bury or Drop in Water
In some cases, adult birds will bury the fecal sacs or drop them in bodies of water. Burying helps decompose the waste naturally and keeps the smell down. It also hides visual signs of nests from predators. Species that nest in burrows or cavities may bury fecal sacs in the walls of their nest. Burying waste near the ocean, a lake, or river can quickly wash away any lingering smell or evidence as well.
Examples of Birds That Bury or Drop in Water
- Atlantic puffins – Drops sacs in ocean
- Bank swallows – Bury sacs in burrow walls
- Grebes – Drop sacs in water
- Storm petrels – Drop sacs in ocean
- Adelie penguins – Flush sacs into sea
Burying and water disposal are convenient methods for species already nesting in underground or seaside spots. It takes minimal effort for adults to maintain cleanliness.
Leave Them or Eat in the Nest
While most bird parents put in effort to remove waste, some species will leave fecal sacs in or near the nest. In these cases, the adults are not as concerned with concealing the nest location. Some cavity nesters fall into this category since their sites are already hidden. Owls and woodpeckers may allow some waste buildup inside nest holes or crevices.
In a few rare instances, the parent birds may actually consume the fecal sacs within the nest. This has been observed in cattle egrets, ospreys, and white ibises. It seems to occur most often when food is very scarce. Eating the waste right in the nest supports the chicks nutritionally but comes with cleanliness downsides.
How Does Waste Removal Vary by Species?
Scientists have documented fecal sac removal techniques in over 300 bird species. While patterns emerge in some groups, examples of nearly all disposal methods can be found across diverse families. Some key differences:
Bird Group | Most Common Fecal Sac Removal Methods |
---|---|
Seabirds like albatrosses and pelicans | Consume sacs or drop in ocean |
Wading birds like herons | Consume, bury, or drop in water |
Raptors like eagles, falcons, and hawks | Consume sacs or drop away from nest |
Songbirds like finches, swallows, and warblers | Carry away and drop at distance |
Cavity nesting birds like woodpeckers, owls, parrots | Carry away, consume, or leave in nest |
As shown, species exhibit diverse waste practices based on their habitat, food availability, nest style, and other factors. But sanitizing the nest area is a universal benefit.
Do All Bird Species Use Fecal Sacs?
While fecal sacs are very common in altricial bird species, some groups do not possess this adaptation. Precocial birds like chickens, ducks, and ostriches have chicks that are mobile soon after hatching. Since the chicks can move around, the parents do not need to collect their droppings. The young birds eliminate waste on their own from a very early age.
Brood parasitic birds like cuckoos and cowbirds are another group that do not manage fecal sacs. Rather than building their own nest, these species lay eggs in the nests of other birds. The host parents end up feeding and caring for the unrelated chicks. But the foster parents only focus waste removal efforts on their own offspring. They usually just let the parasite’s droppings remain in the nest.
A few other bird groups tend not to use fecal sacs:
- Pigeons and doves – Nestlings void runny droppings.
- Bustards – Chicks are precocial and leave nest quickly.
- Tinamous – Voided waste is liquidy and hard to collect.
So while fecal sacs are the norm for most altricial birds, they are absent in some species. But when present, they allow bird parents to maintain clean, sanitary nest conditions.
Do the Chicks Play Any Role?
Bird chicks play a passive but important role in the use of fecal sacs. The baby birds’ physiology and behavior assists the waste removal process. Here are some ways the chicks contribute:
- Their first feces after hatching are enclosed in an egg sac which aids collection.
- Their feces remain thick and gelatinous initially, allowing easy uptake.
- Chicks position rumps toward parents to make waste retrieval easy.
- They restrain defecation until parents are ready to collect.
- Young digest food slowly, minimizing waste frequency.
The chicks’ bodies and actions essentially facilitate sanitary fecal sac usage. This allows the system to work efficiently. The process operates best when parents and offspring play their respective waste management roles.
Conclusion
Fecal sacs represent an ingenious evolutionary solution that supports baby bird health. By containing waste in mucus membranes that parents can transport, dispose of, or consume, nests stay clean and predators remain unaware. Different species utilize the optimal sac removal method for their habitat and constraints. While not universal to all birds, fecal sacs demonstrate the remarkable adaptations that advanced nesting hygiene in numerous groups. The technique is a testament to the power of avian parental devotion and care.