The common blackbird (Turdus merula) is a widespread species whose young require a highly specialized and nutrient-dense diet for survival and rapid development. The early life of a baby blackbird is characterized by an extremely demanding growth rate, which dictates a feeding regimen unlike that of the omnivorous adults. This intense nutritional requirement is only met through a focused diet provided meticulously by both parents.
The High-Protein Diet of Nestlings
The initial phase of a baby blackbird’s life, while confined to the nest, demands an almost exclusively animal-based diet to fuel its rapid growth. During the first few days post-hatching, the food provided is virtually 100% animal matter, emphasizing protein content over all else. This specialized nutrition ensures the quick development of muscle, bone, and feathers in the altricial chicks, who hatch naked and blind.
The primary food sources are soft-bodied invertebrates, which are easily digestible and low in tough chitin. Earthworms are a staple, often constituting the main component of the diet, especially in suburban habitats. Parents also bring caterpillars, soft-bodied larvae, spiders, and low-chitin insects like those from the Diptera and Lepidoptera orders.
The high moisture content of this invertebrate prey, particularly earthworms, is important for the chicks’ hydration. Nestlings cannot leave the nest to drink, so their water intake is entirely dependent on the food delivered by the parents. A prolonged dry spell, which drives earthworms deeper into the soil, can severely impact the quality and quantity of food available.
Dietary Changes During the Fledgling Stage
Young blackbirds typically fledge around 10 to 19 days after hatching, though they remain incapable of independent feeding. Once outside the nest, their diet begins a gradual transition, reflecting evolving digestive capabilities and the start of their foraging education. Parents continue to bring high-protein invertebrates to the fledglings for up to three weeks post-fledging.
During this period, the young birds begin to experiment with non-animal food items, marking the first introduction of plant matter into their diet. This includes soft fruits and berries found in the immediate vicinity of their parents’ territory. The fledglings learn crucial foraging techniques, such as the characteristic head-cocking and ground-hopping used to locate prey, by observing and following the adult birds.
The Critical Role of Parental Foraging
The energy expenditure required by adult blackbirds to feed their young is immense. Both the male and female share the duty of provisioning, working almost non-stop throughout the daylight hours. Their feeding effort increases directly with the size of the brood, meaning a nest of four chicks demands a significantly higher number of foraging trips.
The parents prepare the food, often using their digestive systems and saliva to ensure it is in a suitable, easily-swallowed state for the chicks. The adults also meticulously remove fecal sacs from the nest to maintain hygiene.
This intensive parental care extends well beyond the nest stage. If the female begins a second clutch of eggs, the male blackbird often assumes sole responsibility for feeding the recently fledged young for several weeks.