What is one key characteristic of all protected birds in Illinois?

One key characteristic of all protected birds in Illinois is that they include all native species. This means that the emphasis is on the conservation of birds that are indigenous to the state, ensuring the protection of their habitats and populations. Protecting native species is essential for maintaining biodiversity and ecological balance within the region. It reflects a broader commitment to safeguard the natural heritage of Illinois by recognizing the important roles these birds play in their ecosystems.

The other choices do not accurately reflect the characteristics of protected birds. For example, non-native species may not be protected as they can have detrimental effects on local ecosystems. Similarly, size is not a determining factor for protection status, and the ability to swim does not apply to all protected birds, as many species do not inhabit aquatic environments. Therefore, focusing on the inclusion of all native species captures a fundamental principle of wildlife conservation efforts in Illinois.