There appears to be a pattern with the Kosher food laws in Leviticus 11. Flying creatures only have to be herbivores, and land creatures that were herbivores that chewed cud (regurgitated grass) and had split hooves were considered clean. It seems that land and air creatures that were omnivores, carnivores, and scavengers were all classified as unclean. This may have be connected to why humans are forbidden from consuming blood as moral sin in the bible (Genesis 9:4, Lev 7:25-26, Lev 17:10-14, Lev 19:26, Deut 12:16, Deut 12:22-25, Deut 15:23, Acts 15:20 & 29). What if animals that eat meat (who consume blood), are classified as sinful in a sense because they don’t drain the blood? Land creatures are even further distinguished by diet (cud-chewing herbivore) and anatomy (split hooves), which may clue into their digestion processes. For example, rabbits are cud chewers but they also eat their own dung, which is something that may be viewed as unclean.
Sea creatures aren’t limited by diet because the focus is on anatomy. Sea creatures are only required to have both scales and fins to be kosher, and since fish with fins and scales can eat meat the blood issue must not be a problem here. This could be because the blood spills out and is diffused into the water and is not consumed as much. Also, fish scales limit the absorption of poisons and toxins in the water, which protects those fish from becoming toxic. Another thing to notice is that in the Bible, sea creatures were never sacrificed. This is most likely because fish are not commodities, since they live in the water and can’t be farmed or held as investments. There also may be a spiritual aspect to it. A person doesn’t have to ‘kill’ a sea creature, it simply dies when you take it out of the water. I suspect that since the taking of life is not experienced like with an air-breathing animal, it doesn’t have the same effect of showcasing the darkness of sin through slaughter. From what I’ve read online, it seemed pretty rare that cultures sacrificed fish. I found that ancient Taoists and Greeks sometimes sacrificed fish, but not much else.
The clean animals were sacrificed for the sins of humans, so one needs a pure/clean (sinless) animal for sacrifice to take on the sins of the person. So animals that eat other animals (dead or alive) are possibly seen as being in a “sinful” state because they consume blood. Land herbivores like some mammals (rabbits), as well as reptiles and amphibians, are unclean since they don’t meet the anatomical requirements. Plus, creatures that are venomous or poisonous would be off-limits and many reptiles fit this description. There are some mammals like certain types of shrews, moles, and bats that are toxic. Some creatures eat things that can make them poisonous at certain times, meaning they can be considered clean but need to be cooked a certain way as a precaution. Many poisonous birds fit in this category like Spur-Winged Goose, Hooded and Northern Variable Pitohui, and even Quail. Overall, the anatomy restrictions seem like a way of warning the Israelites about food safety without getting into specifics for each creature.
Quail specifically can cause a sickness that we see in the bible in Numbers 11:31-34 called coturnism. This sickens became so widespread throughout the Mediterranean that the Roman Empire officially banned the eating of quail in the 1st Century CE. It is said that quails are not always poisonous and this toxicity may come from something Quails eat, possible candidates being hemlock, Hellebore, or woundwort. Quail is kosher since it is not mentioned in Leviticus 11, and it was already given by God as food in Exodus 16, so cleanliness wasn’t an issue. Typically poisonous or venomous creatures are in the category of unclean. The poisoning is limited to Numbers 11, and the bible says this is because of the Israelites’ sinful attitude towards God, so this is a unique event. The Israelites called the place of the poising Kibroth-hattaavah (graves of the gluttons), so maybe because the people that died were especially gluttonous? It could be that their quail wasn’t cooked right (because those people rushed it), or those people simply ate too much of it causing toxicity and coturnism. Also, it is possible a flock of toxic quail joined the flock of safe quail and those wicked people simply got the bad ones. Since everyone didn’t die so God spared the righteous and therefore there must have been a distinction among the quail or a distinction between how the people prepared/ate it.