: They undergo a "thermoregulatory metamorphosis" over approximately 12 days , transitioning from an ectothermic-like state to being able to maintain their own body heat.
: They typically breed in marshlands, wetlands, or grassy areas near water, with females building deep cup-shaped nests lashed to reeds like cattails. Species Profiles yellow-souldered blackbird revised recovery plan - FWS ECOS agelaius
: A single male often defends a territory containing a "harem" of up to 15 nesting females . or grassy areas near water