fight between two American Coots, with a non-combatant onlooker that appears in photos 2-4. The fighting went on for about 20 minutes. The onlooker arrived shortly after the fight began and remained near the scene throughout.

The Merlin Sound ID AI says it heard a wood thrush near the end of this recording. Can an experienced birder check it? Sometimes I can hear internal forest birds like that in this area in the summertime.

Heartbreak
It is very possible this egret is the mate of the dead one and was trying to confirm that its partner is indeed dead. This would not be a food situation because great egrets swallow their meals whole and obviously any birds they would eat, would be much smaller. I ran this photo by some bird experts and they agree, this is probably the dead bird's mate. Heartbreak in the rookery.

Male. Link to female Costa's Hummingbird for comparison: https://www.inaturalist.org/observations/144261929
Link to observation of dozens of Costa's peacefully sharing hummingbird feeders: https://www.inaturalist.org/observations/144476737

Costa's Hummingbird (Calypte costae) Male has purple head and long extended dark purple gorget that looks often looks black. Female has a pale postocular stripe that connects to side of neck. This distinguishes it from female Black-chinned Hummingbird (Archilochus alexandri) that looks very similar. "Black-chinned leave the (desert) area in September and return in April, while Costa's are present year round." D. Rankin. Costa's avoid the hot summer by migrating to coastal California and Baja California.
Conservation Status: Vulnerable in California. A desert adapted hummingbird. Common but numbers have declined where desert is cleared for development. In some places it has adapted to nesting in suburbs. Natural desert habitat: washes, stream sides, sage scrub, mostly in dry and open places having a good variety of plant life.
Diet is mostly nectar and insects. Takes nectar from flowers, and will feed on tiny insects as well. Looks for nectar on desert native plants such as agave, chuparosa, desert honeysuckle, and fairy-dusterill and also feed on sugar-water mixtures in hummingbird feeders. 4:1 (or even 3:1) is a good ratio of water to sugar. Change the solution at least weekly before it gets cloudy or moldly and Never add red dye!
The thin, high-pitched whistle of the male Costa's is often heard over desert washes in early spring. Sound recordings below.

National Geographic Field Guide to the Birds of Western North America, ed. Jon L. Dunn, 7th ed., 2017, pp. 96-97.

Audubon Guide to North American Birds https://www.audubon.org/field-guide/bird/costas-hummingbird

Bird Songs and Sounds I.D. worldwide https://xeno-canto.org/explore?query=Calypte%20costae

Found Feathers: https://www.fws.gov/lab/featheratlas/idtool.php