Sources and further reading

Every page carries its own sources. This is the standing list, and a short guide to which one to ask when you have a question we have not covered.

Updated September 7, 2026·3 min read

The short answer

For species biology, range and diet, the Cornell Lab of Ornithology's All About Birds is the first place to look.
For anything about disease at feeders, use the USGS National Wildlife Health Center and your state or provincial wildlife agency, in that order.
For questions about local law, feeding bans, trapping and nest management, only your state, provincial or municipal authority can answer.
For a sick, injured or orphaned bird, find a licensed wildlife rehabilitator. No website is a substitute.

Every page on this site lists the sources behind it at the foot of the page. This is the standing list: the organizations we draw on repeatedly, what each is actually good for, and how to use them directly when your question is more specific than anything we have written.

Species biology, identification and diet#

Cornell Lab of Ornithology, All About Birds. The reference for North American species accounts. Range maps, identification, diet, behavior, sound recordings, life history. If you want to know what a bird eats away from feeders, or whether it occurs where you live, start here.

Cornell Lab of Ornithology, Project FeederWatch. A long-running citizen science program in which thousands of participants count birds at their feeders through the winter. Its public material on feeder types, common feeder birds and feeder maintenance is the closest thing to a standard reference for this subject, and it is the primary source behind much of our feeder and preference material.

National Audubon Society. Species guides, habitat and conservation material, and practical guidance on attracting birds, plus a network of local chapters that are often the fastest route to a knowledgeable person near you.

Birds Canada. The Canadian counterpart, including Project FeederWatch in Canada. Use it in preference to US sources for Canadian range, timing and regulation.

Disease, health and safety#

USGS National Wildlife Health Center. The authority for wildlife disease in the United States. Its bulletins are where salmonellosis, avian influenza and similar outbreaks are announced, and they are the basis for the take-your-feeders-down advice on our diseases at feeders page.

Your state or provincial wildlife agency. The one source that can tell you what applies where you live: current outbreak advisories, bear country rules, feeding restrictions, whether a species is protected locally, and which wildlife rehabilitators are licensed near you. Their guidance overrides anything on this site.

Licensed wildlife rehabilitators. For a bird in front of you that is sick, injured or orphaned. Find one through your state agency's list rather than through a search engine.

Law and regulation#

Wildlife law in North America operates at several levels, and general advice is worth very little here. The Migratory Bird Treaty Act protects most native birds in the United States, with a small number of introduced species excluded; Canada has parallel legislation. On top of that sit state, provincial and municipal rules that may restrict feeding entirely, particularly where bears or rats are a concern.

If your question begins "am I allowed to", the answer comes from your wildlife agency or your municipality, not from us. We say so on the pages where it matters, including bears, house sparrows and hawks at feeders.

Nutrition and composition data#

USDA FoodData Central. The source of the energy, fat and protein figures in our nutrition table and, by extension, the cost per calorie analysis. Composition values there are for the kernel or the product, which is why our tables apply a separate kernel yield correction, explained in the methodology.

University extension services#

State university extension services publish some of the most practical material available on feeder hygiene, seed storage, pest management and regional plant selection, and it is usually written for exactly the audience this site serves. Search for your state's extension service followed by the topic. Quality is consistently high and it is free.

How we use these#

Our editorial standards set out the order of authority: agencies and peer-reviewed research first, established ornithological institutions second, standard reference data third, and our own derived analysis last and always labeled as ours. We do not source claims from retailers, manufacturers or other bird feeding sites.

Where a claim on this site is not sourced, it is because we could not source it and chose to write the guidance without a citation rather than attach one that does not support it. Where our own analysis goes beyond the sources, the methodology shows the working.

Frequently asked questions#

Which single source should I bookmark?

All About Birds, from the Cornell Lab of Ornithology, for species questions, and Project FeederWatch, from the same institution, for feeder-specific questions. Between them they answer most of what a feeder owner needs, they are free, and they are maintained by the largest ornithological research program in North America.

Why do you link to organization sections rather than deep pages?

Because deep URLs move and a broken citation is worse than a general one. We link to the section of a site that holds the relevant material, which stays stable, and name the specific document in the citation text so you can find it even if the address changes.

How do I find my state wildlife agency?

Search for your state or province followed by department of natural resources, department of fish and wildlife, or wildlife agency. Every US state and Canadian province has one, and each maintains guidance on feeding wildlife, bear country rules, disease outbreaks and lists of licensed wildlife rehabilitators. Their rules override general advice, including ours.