<p>Reproductive success in birds is shaped by parental care, nest characteristics, thermal conditions, and habitat context, yet detailed information remains scarce for many Neotropical taxa, including hummingbirds. We studied the reproductive biology of the <i>Saucerottia beryllina</i> (berylline hummingbird), one of the most abundant hummingbird species in Mexico City, to describe nest structure, maternal care, nest thermal conditions, and survival across the breeding cycle. Fieldwork was conducted using systematic nest searching and focal observations. Maternal time investment per behavioral bout (incubation, off-nest, and feeding) was quantified across nesting stages, egg and nestling temperatures were measured using thermal imaging, and nest structure and materials were characterized after breeding. We analyzed 25 nests, which were open cup–shaped, constructed with a combination of plant-derived and anthropogenic materials, and placed at a mean height of 3.95 ± 1.05&#xa0;m on a variety of substrates. Maternal time allocation varied significantly among activities and nesting stages: females spent longer incubation bouts during the egg stage and progressively increased off-nest time during the nestling stage, while feeding bouts remained short throughout development. Egg and nestling temperatures were significantly higher than ambient conditions, remaining on average ~ 19&#xa0;°C above environmental temperatures, indicating effective thermal regulation. Nest survival was highest during the egg stage and declined markedly as nestlings approached fledging, with significantly lower survival at the more disturbed study site. These results reveal stage-specific shifts in maternal investment and context-dependent patterns of nest survival in urban and semi-natural habitats. This study provides baseline reproductive data for <i>S. beryllina</i> and contributes to understanding hummingbird reproduction in human-modified landscapes.</p>