Eastern Bluebirds are full of surprises, and one of their lesser-known habits is the efficient removal of fecal sacs. I recently photographed a male Eastern Bluebird performing this cleanup task outside one of my nest boxes.
What Is a Fecal Sac?
A fecal sac is a mucous membrane that surrounds the waste produced by nestlings. It looks white or clear and keeps the mess contained, making it easier for the parents to remove. This behavior helps keep the nest clean and reduces the risk of attracting predators.
How the Process Works
When a nestling is ready to pass waste, it lifts its rear and signals the parent. The adult bird then collects the sac and flies off to discard it away from the nest. From what I’ve observed, the parents usually remove one or two sacs per hour. This cleanup often happens right after feeding.
Why It Matters
This behavior isn’t just about hygiene. Fecal sac removal reduces scent and visual cues that could give away the nest’s location. Some bird species even consume the sacs, possibly for nutrition. Nestlings usually stop producing fecal sacs shortly before they fledge.
Camera Settings and Setup
To get this shot, I stayed inside my vehicle to avoid disturbing the birds. I used a Fujifilm X-T3 with a Canon EF 100-400mm f/4.5-5.6L IS II lens, paired with a Fringer EF-FX Pro adapter. The camera rested on a bean bag on the window. Here are my settings:
- Shutter Speed: 1/220 second
- Aperture: f/5.6
- ISO: 2500
- White Balance: Auto
You can read more about my technique here: My Eastern Bluebird Photography Setup
Final Thoughts
The Eastern Bluebird’s fecal sac routine may not be glamorous, but it highlights just how well-adapted these birds are to raising clean, healthy chicks. It’s one of many fascinating behaviors I’ve observed while photographing wildlife.
For more insight into this topic, I recommend this article by Audubon: What Are Fecal Sacs? Bird Diapers, Basically