Bulbul birds are small perching songbirds that belong to the family Pycnonotidae. There are over 130 different species of bulbul found across Africa, Asia and the Middle East. These sociable birds are known for their loud, musical calls and for their inquisitive nature. Many species of bulbul live in densely vegetated habitats and can be challenging to spot amongst the foliage. However, their distinctive vocalizations often give away their presence.
One interesting fact about bulbuls is that they build remarkably flimsy nests, considering they typically lay between 2-5 eggs in a single clutch. The nests are cup-shaped and composed of fine twigs, roots, grasses and leaves. They are lashed together rather haphazardly and lined with soft materials like feathers or shredded bark. Given the precarious nature of their nest construction, it seems miraculous their eggs don’t go tumbling out! But somehow these nests suffice to cradle the bulbul’s small brood of eggs.
In this article, we will take a closer look at the nesting habits of bulbul birds and the typical clutch sizes of different bulbul species. We will examine why the number of eggs can vary and what factors influence brood size. We’ll also look at how both parents cooperate to incubate the eggs and raise the demanding chicks. Finally, we’ll overview how many broods bulbul pairs may raise in a single breeding season.
Typical Clutch Sizes of Different Bulbul Species
Bulbul clutch sizes can range from just 2-3 eggs in some of the smaller species, up to 4-6 eggs in some of the larger bulbuls. Here are some examples of typical clutch sizes for common bulbul species:
Red-whiskered Bulbul
The red-whiskered bulbul is a slim, graceful songbird found across Asia. It builds a flimsy cup nest and lays a clutch of 3-5 eggs. Modal clutch size is 4 eggs.
Red-vented Bulbul
The red-vented bulbul inhabits scrub and gardens across the Indian Subcontinent. It builds a loose nest and lays a typical clutch size of 2-4 eggs. Modal clutch size is 3 eggs.
African Red-eyed Bulbul
The African red-eyed bulbul is found in sub-Saharan Africa in woodland and forest habitats. It constructs a cup nest and lays 2-4 eggs per clutch. Modal clutch size is 3 eggs.
Common Bulbul
The common bulbul is distributed across eastern Africa and the Middle East in semi-arid regions. It builds a flimsy nest and lays a clutch of 3-5 eggs. Modal clutch size is 4 eggs.
White-eared Bulbul
The white-eared bulbul inhabits wooded areas across southeast Asia. It builds a loose nest and lays a clutch of 2-4 eggs. Modal clutch size is 3 eggs.
As we can see, the modal or most common clutch size for most bulbul species falls between 3-4 eggs. However, there is variation across the bulbul family, with smaller species tending towards smaller clutches with fewer eggs. Larger bulbuls may lay up to 6 eggs on occasion.
Why Does Clutch Size Vary?
There are a few key factors that account for the differences in clutch size between bulbul species and even between individuals:
Body size
Larger bulbul species can physically accommodate larger clutches, while smaller species are constrained by body size. A petite female red-whiskered bulbul likely could not successfully incubate 6 large eggs like the bigger common bulbul can.
Geography & climate
Bulbuls living in regions with abundant resources and extended breeding seasons can afford to raise more offspring per clutch and more broods per year. Bulbuls in harsher, seasonal climates may max out at fewer eggs per clutch and fewer broods per year.
Age of parents
Older, more experienced bulbul pairs often lay larger clutches than younger first-time breeders. Their skill helps them succeed with raising more demanding broods.
Food availability
When food is plentiful, bulbuls can gather enough resources to sustain larger clutches. When food is scarce, they conservatively limit clutch size.
Predation levels
In areas with heavy nest predation, smaller clutches may enhance survival odds rather than large clutches that draw attention.
So in optimal conditions, older bulbuls in resource-rich environments with low predation can raise the largest broods. But reproduction is modulated based on circumstances.
Incubation and Chick Rearing
Once the clutch is complete with 2 to 6 eggs, incubation begins. In most bulbul species, both parents participate in incubating the eggs. The female typically incubates at night, while the male takes over during the day. Incubation lasts about 14 days before the altricial chicks hatch.
The chicks are blind, naked and helpless at birth. Both parents share equally in feeding and brooding the chicks. In the first week, the chicks need almost constant feeding as they grow rapidly. The parents work hard to keep up with demand, flying back and forth gathering caterpillars, insects, fruit and nectar.
As the chicks age, their appetites remain voracious. They keep the parents busy finding enough food from dawn to dusk. The chicks fledge the nest at around 3 weeks old, but remain dependent on their parents for an additional 2-3 weeks. Throughout the rearing process, the diligent cooperation of both bulbul parents is essential to successfully raise a clutch – whether it contains just 2 tiny chicks or a brood of 6.
Number of Broods Per Season
Most bulbul species are capable of raising multiple broods per breeding season, especially where habitat conditions allow for an extended season. Some examples:
Red-whiskered Bulbul
Can raise up to 4 broods per year
Red-vented Bulbul
Can raise up to 3 broods per year
African Red-eyed Bulbul
Can raise up to 2-3 broods per year
Common Bulbul
Can raise 1-2 broods per year
So the potential reproductive output for a bulbul pair in a single year is substantial, easily ranging from 4-20 offspring depending on habitat, resources and the number of broods. This high reproductive potential is important since bulbuls face heavy predation pressure at all life stages. However, not all hatchlings will survive to adulthood and breeding age.
Conclusion
Most bulbul species lay clutches containing 2-4 eggs, with modal clutch size averaging 3-4 eggs. Some factors influencing clutch size include body size, climate, age, food availability and predation pressure. Both bulbul parents incubate eggs and raise demanding altricial chicks that require diligent care. Given extended breeding seasons and high reproductive potential, a bulbul pair can raise up to 4 broods a year. Their loose nests seem to suffice despite large seasonal outputs of eggs. With plentiful food, diligent parenting and a bit of luck, bulbuls can overcome risky nest sites and heavy predation to successfully raise new generations of fledglings.