Host preference plays an important role in the transmission cycle of mosquito-borne pathogens and can be determined by analyzing the blood meals of mosquitoes. For the present study, 398 blood-fed female mosquitoes collected throughout Germany from 2016 to 2022 were successfully examined for the origin of the blood meal, using two PCR approaches sensitive to various vertebrate groups. The first approach targeted a conserved 16S rDNA region of the cytochrome c oxidase subunit 1 gene; the second approach was only carried out if the first produced no result. The study included 27 mosquito taxa from five genera and identified 50 vertebrate species as hosts: 24 bird, 23 mammal (including humans), two reptile, and one amphibian species. Contrary to common assumptions, Culiseta morsitans/fumipennis showed regular feeding on mammals (including humans) despite its described ornithophilic nature. Similarly, Culex pipiens biotype molestus, previously thought to be highly mammalophilic, fed frequently on birds. Data on the hybrids of the Cx. pipiens biotypes confirmed an indiscriminate biting behavior. Culex pipiens biotype pipiens showed a less stringent preference for birds than expected; however, the preference among avian hosts was clearly for European blackbirds (Turdus merula). Overall, the results argue for a host selection directed by availability in addition to innate preference. These results emphasize the need for further investigations into mosquito host preferences in Germany to better understand disease transmission dynamics.