Discovering a bird egg outside its nest often prompts questions about its viability and what actions to take. This article provides practical guidance on assessing a bird egg’s potential for life and outlines appropriate steps to ensure the well-being of local wildlife.
Methods for Checking Viability
Candling determines if a bird egg is alive. Shine a bright flashlight through the egg in a darkened room, holding it gently. A viable egg often shows a network of fine, spider-like blood vessels radiating from a central dark spot, indicating a developing embryo. As the embryo matures, it may appear as a larger, opaque mass, and sometimes slight movement is visible.
The air sac, typically at the wider end, also provides clues. It appears as a distinct, clear area and generally expands as the embryo develops. Perform candling quickly and with extreme care to avoid disturbing the embryo or causing temperature fluctuations. Not all eggs show clear signs of development, especially in early stages.
The floating test involves placing the egg in water. A fresh, non-viable egg typically sinks, while an older, viable egg may float upright due to a larger air sac. However, this method carries significant risks. Sudden temperature changes can harm a developing embryo, and water absorption through the shell can lead to bacterial contamination. For these reasons, the floating test is not recommended due to its potential to damage viable eggs and its lower reliability compared to candling.
Visual cues and odor can also indicate a non-viable egg. A foul smell suggests it is rotten. Similarly, a cracked, discolored, or shriveled eggshell indicates it is unlikely to be viable. However, the absence of these signs does not definitively confirm viability, making candling the most informative and least intrusive assessment technique.
What to Do Next
If candling suggests the egg is viable and it fell from an identifiable nest, carefully return it. Birds generally do not abandon eggs or chicks simply because a human has touched them, as their sense of smell is not as developed as their visual or auditory senses. If the original nest is inaccessible or cannot be located, create a makeshift nest in a small container, such as a berry basket, and secure it near where the egg was found.
Place soft nesting material, like dry grass or leaves, in the container. Position it securely in a tree or shrub where parent birds might find it. Observe from a distance to see if the parent birds return. If they do not return within a few hours, or if the situation seems complex, contact a local licensed wildlife rehabilitator or rescue organization. These professionals possess the expertise and permits to properly care for wild bird eggs and chicks.
Conversely, if the egg shows no signs of viability after candling, or is clearly broken or rotten, do not return it to a nest. In such cases, dispose of the egg according to local regulations, or leave it in place. Non-viable eggs can decompose naturally or be consumed by scavengers, returning nutrients to the ecosystem.
Important Considerations
Handling wild bird eggs is often subject to legal protections designed to conserve bird populations. In the United States, the Migratory Bird Treaty Act (MBTA) makes it illegal to possess, collect, or disturb most wild bird eggs, nests, or birds without a permit. Similar laws exist in many other countries. Therefore, approach any intervention with caution and awareness of these regulations.
Beyond legal aspects, safety and hygiene are important when interacting with wildlife, including bird eggs. Bird eggs can carry bacteria like Salmonella, transmissible to humans. Avoid direct skin contact by using gloves or a barrier, and thoroughly wash hands with soap and water after any contact. Minimizing handling time also reduces stress on a potentially viable embryo and lessens disease transmission risk.
The general principle when encountering wild animals, including bird eggs, is non-intervention unless necessary. Not every egg is destined to hatch; natural mortality is part of ecological balance. If uncertain about the best course of action, or if the situation requires more than simple observation, contact a licensed wildlife rehabilitator. These experts provide tailored advice and can intervene in a manner that complies with legal and ethical standards for wildlife care.