Sociable Weaver (Philetairus socius) Fact Sheet: Reproduction & Development

Courtship

• A male persistently follows a female (from Collias and Collias 1978)
• Proximity to female
• Stays within 0.5-1.5 m (1.6-4.9 ft) of her, never straying for more than a few moments
• Body posture
• Body held nearly erect, the tip of his tail touching the ground/substrate; feathers pressed to the body giving a sleek, trim appearance
• Deliberately flips the tail over his back and down again
• Male may pace in front of female with bill upturned as the tail points to the ground
• Nest material often held in his beak
• Mated pairs form extended bonds (from Paquet et al. 2015 unless otherwise noted)
• “Divorce” uncommon in one study; occurring twice over one 5 year observational period

Copulation

• Occurs within nest chambers, most often (Maclean 1967; Collias and Collias 1978)

Year-round reproduction (from Maclean 1967 unless otherwise noted)

• Reproduction commonly occurs in summer (Altwegg et al. 2014; Covas et al. 2008)
• Rainfall associated with reproductive timing
• Duration of breeding seasons likely dependent on green plant growth after rain events

Nest architecture  (from Maclean 1967; Maclean 1973b unless otherwise noted)

• General structure
• Multiple nesting chambers built below an over-arching roof; construction rests on horizontal branches or supports
• Entire structure known as a nest mass
• A tree may contain more than one nest mass
• Nest masses and inhabitants collectively referred to as a colony
• Construction materials
• Roof
• Small sticks, 10-30 cm (3.9-11.8 in) in length; thorny twigs
• Body of nest
• Grass straw
• Fresh, green blades form the chamber entrance
• Horizontal support
• Typically a tree branch with unobstructed access from below
• Camelthorn tree, Vachellia eroloba [formerly Acacia erioloba], is commonly used
• Telephone poles or water towers used on occasion
• Size
• Among the largest nest constructed by birds (van Dijk et al. 2013)
• Largest recorded nest mass: c. 7 m (23 ft) in diameter
• Varies with age of the structure
• Birds continually add new materials
• May take up most of a tree’s canopy
• Limited by the size of the tree/support
• Nesting chamber features
• Shape rounded with a single entrance tunnel
• c. 15 cm (5.9 in) in diameter
• Tunnel entrance vertical and narrow
• 6-7 cm (2.4-2.8 in) wide
• Up to 25 cm (9.8 in) in length
• Set to one side of the tunnel
• Thickly lined with soft, dry materials
• Floor, roof, and sides receive padding
• Insulated with seed heads (of grasses), furry leaves, shredded grass blades, feathers (on occasion), and bits of cotton or wool cloth
• 5-50+ chambers/nest mass
• No interconnection between chambers in the same nest mass

Nest construction  (from Maclean 1967; Maclean 1973b unless otherwise noted)

• Stages of construction
• Begin with nest mass foundation
• Collect loose grass blades one at a time, and carry to the construction site
• Anchor grass into rough bark or between twigs on terminal branches
• A conical or pyramidal shape begins to form
• Addition of  nest chambers
• Locate new chambers on the structure periphery as the nest mass continues to grow
• Initially build chamber interior; the structure grows outwards
• Tuck lining into the chamber prior to completion of the outer walls
• Add entrance tunnel when nest chamber is nearly complete
• Tunnel continues to grow as the nest mass increases in size; length no more than 25 cm (9.8 in)
• Roof laid on top of nest mass
• Builders/Participants
• All colony members cooperate to build the foundation and nest chambers, though members tend to concentrate efforts on a given area of the nest mass
• Males focus efforts on the outside more than do females (van Dijk et al. 2014)
• Within the breeding season only the breeding pair maintains their chamber

Nest longevity and function

• Suitable trees may be continually used for long periods (from Maclean 1967)
• >100 years
• No apparent damage to trees
• Thermoregulatory benefits
• Buffers against temperature fluctuation (van Dijk et al. 2013; White et al. 1975)

Clutch characteristics

• 2-6 eggs per clutch (Craig 2004; Maclean 1967)
• Typically 3-4 (Maclean 1967)
• 24 hour interval between laying of each egg (Maclean 1967)

Egg characteristics

• Shell dull white; densely spotted with shades of gray
• More densely packed at the thick end (Maclean 1967)
• Egg size
• 18.1-22.8 mm (tall) x  13.2-15.9 mm (wide) (0.7-0.9 in x 0.5-0.6 in)
• 1.9-3.0 g (0.07-0.11 oz) (Paquet et al. 2013)
• Mass of eggs decreases with the presence of non-breeding helpers within a colony

Incubation

• Begins with laying of the second egg in a clutch, most often (Maclean 1967)
• Mother and father “sit” on eggs, though male contribution is variable and typically less than that of the female (Craig 2004)
• Eggs seldom left uncovered (Maclean 1967)
• Duration
• 13-15 days (Covas et al. 2008; Craig 2004; Maclean 1967; Maclean 1973c)

Hatching

• Clutch mates asynchronously hatch (Paquet et al. 2013)

Interclutch interval (time between consecutive clutches) (from Maclean 1973c unless otherwise noted)

• Reproduction tied to success or failure of first reproductive effort and rainfall (Maclean 1973c)
• Lay multiple clutches each in some reproductive periods (Covas et al. 2008)
• As many as 8 clutches (Covas et al. 2008)
• Reports of up to 15; though this record was associated with the production of unsuccessful clutches due to nest predation by snakes and an exceptionally long breeding season (R Covas personal communication)
• Within 2 weeks of successfully brooding a clutch, though timing is variable (Covas et al. 2008; Maclean 1973c)
• Produce a replacement clutch quickly following an unsuccessful brooding attempt (Maclean 1973c)
• Within one week; as early as 2 days following loss of a clutch (Maclean 1967)

Nestlings (from Craig 2004 unless otherwise noted)

• Appearance
• Naked; skin pink
• Eyes closed
• Mouth
• Gape swollen and creamy-white (Maclean 1967)
• Yellow inside mouth
• Care
• Fed by both parents, though non-parental birds and older, fledged siblings may also provide food (Craig 2004; Maclean 1967)
• Offered insects and insect larvae (Maclean 1967)
• Gradual change from small, soft insects to larger ones (e.g. grasshoppers, moths, mantids, and net-wings)
• Given only animal foods until independent of adults
• Development
• Eyes open c. 7-10 days of age
• Feathers emerge from sheaths c. 14 days of age
• Fledge 21-24 days
• Clutch-mates typically fledge on or near the same day (Maclean 1967)
• Mass of fledglings
• c. 18-35 g (0.6-1.2 oz) (Paquet et al. 2013)
• Dependent on care more than 2 weeks after leaving the nest

Adults

• Obtain adult plumage c. 4 months of age (Brown et al. 2003)
• Fidelity to natal (birth) colony (from Covas et al. 2006)
• Females tend to disperse
• Males tend to remain within their birth colony throughout life
• Older individuals tend to secure nest chambers near the center of a nest mass (Van Dijk et al. 2013)

Wild populations

• Not reported

Managed care

• Median life expectancy
  • No AZA estimates

Predators (from Maclean 1967 unless otherwise noted)

• Predation risk high
• Nest predators
• Cape cobra (Naja nivea) and boomslang (Dispholidus typus) (Maclean 1967; Spottiswoode 2007)
• Primarily target chicks (Maclean 1973d)
• A single snake is capable of eating all chicks in a single nest mass (Maclean 1973d)
• Honey badger (Mellivora capensis)
• Aerial and canopy predators
• Chanting (Melierax musicus) and Gabar (Micronisus gabar) goshawks
• Likely predators
•  Falco spp: Rock and Greater kestrels, Red-necked and Lanner falcons
• Terrestrial predators
• Yellow mongoose (Cynoctis penicillata)
• Possible predators
• Caracal (Felis caracal), Cape wild cat (F. lybica), and red mongoose (Myonax ratlamuchi)

Survival rates

• Adults and juveniles have similar rates of survival (Covas et al. 2004b)

Birds build communal nests in trees or on other large structures. These apartment-like structures are among the largest nests built by birds. The image above was taken at the San Diego Zoo and represents a single nest mass. A single tree may contain multiple nest masses each of which houses numerous nest chambers that are used for reproduction and roosting.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Altwegg et al. (2014)
Brown et al. (2003)
Collias and Collias (1978)
Covas (2012)
Covas et al. (2004b)
Covas et al. (2006)
Covas et al. (2008)
Craig (2004)
Maclean (1967)
Maclean (1973b,c,d)
Paquet et al. (2013)
Paquet et al. (2015)
van Dijk et al. (2013)
van Dijk et al. (2014)
White et al. (1975)
ZIMS (2014)