One brand of American dish soap, Dawn, has a duckling as a mascot, and has for some years advertised its grease-cutting capability (and gentleness on living things) by showing that it is used to clean oil off waterfowl who have been caught in a slick.
One brand of UK dish soap, Fairy Liquid, bears the label "H412 - Harmful to aquatic life with long lasting effects"
https://www.newhall.co.uk/media/7440_msds.pdf
The H412 comes from sodium laureth sulfate (SLES) which is contained (in large amounts, like 20 to 70% by weight) in practically every kind of liquid soapy detergent, shampoo, liquid hand soap and what not. The only reason you know of that one product is that they seem to sell to professionals as well, which is why they need a material safety data sheet. Your shampoo doesn't need that, so you just don't know that it is just as harmful.
Edit: Dawn seems to contain it as well, look for CAS# 68585-34-2: https://msdsdigital.com/system/files/Dawn_Professional_Dish_... The missing H- and S-numbers in that datasheet come from the differing standards and maybe the different concentrations.
It's in all sorts of crap, not just soap. Hand lotion, toothpaste, etc. I'm unlucky enough to be allergic to it, my skin blisters & peels off after touching even rather small quantities. Finding safe cleaning & hygiene products (especially toothpaste) was difficult, but thankfully there are some brands that started producing sulfate-free products for the new-age free-range organic everything crowd, so it's been getting easier.
ACS's Chemical of the Week for October 24, 2017.
https://www.acs.org/molecule-of-the-week/archive/s/sodium-la...
So use solid soap / shampoo for outdoors (check usability first, naturally).
Solid soap isn't any better. All of those work by making fats water-soluble. This destroys mucous membranes and skin slime layer of fish and other animals and breaks down lipid barriers of algae and bacteria.
The real takeaway is that concentration matters a lot: one person washing up for the morning won't kill a pond, but a hundred people or prolonged exposition will.
That's just to emphasise the fact that you don't use fairy liquid to clean ducks. You use it to clean fairies.
Likewise toilet duck toilet cleaner is just a brand name. You use it for cleaning duck toilets not ducks themselves. And don't get me started on duck tape. One honest mistake and it's a lifetime ban from the RSPB.
Yes; don’t wash your pet halibut with it. Don’t think it should be dangerous to birds, tho.
Fairy dish soap is the European version of Dawn. I'd be surprised if the formulation were significantly different.