| Australian mudnesters | |
|---|---|
 | |
| White-winged chough (Corcorax melanorhamphos) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Superfamily: | Corvoidea |
| Family: | Corcoracidae Mathews 1927 |
| Species | |
| Synonyms | |
StruthideidaeMathews 1924 | |
Corcoracidae is a family ofpasserine birds known as theAustralian mudnesters. The family has sometimes been calledStruthideidae in the past; however, despite Struthideidae being an older name than Corcoracidae, the latter name takes precedence.[1] It contains just twospecies in two genera, thewhite-winged chough (Corcorax melanorhamphos) and theapostlebird (Struthidea cinerea). Both are endemic toAustralia.[2]
Both the Australian mudnesters are found in openhabitat in eastern Australia, mostly openeucalypt woodlands and some forest that lacks a closed canopy. The apostlebird is more tolerant of arid habitats and is found in aridwoodland andshrublands. Both species are tolerant of human modifiedhabitats and will occupyfarmlands and suburban areas, and even parks and gardens.[2]
The two mudnesters are medium-sized passerines, the apostlebird being smaller at around 31 centimetres (12 in) in length and the larger white-winged chough averaging 47 centimetres (19 in). Their morphology is typical of ground feeding passerines, with long legs and short, rounded wings. The most noticeable differences between the two species are in theplumage (grey with brown wings and a black tail in the apostlebird, and black with white wing patches in the white-winged chough) andbill shape.[2] The bill of the apostlebird is short and deep, not unlike that of afinch, whereas the bill of the white-winged chough is long and curved, not unlike that of its Old World namesakes, thechoughs. The differences in the bills reflect the differences in feeding ecology, with the apostlebirds using theirs for sparrow-like picking whereas the white-winged chough uses its bill to flick leaf litter around.[3]
In the field, the relationship between the two species is immediately apparent: both species are highly social, spending much of their time foraging through leaf litter with a very distinctive gait, calling to one another almost constantly. Both species respond to a human interloper by flying heavily to a nearby tree, where they wait for the disturbance to pass, often perching close together in twos and threes andallopreening. In picnic grounds and parks these birds may become accustomed to humans and become very tame.[2]
The social groups of mudnesters are based around a dominant male and female. The number of birds in the group may vary from two to twenty birds, six birds being typical in the white-winged chough and seven to nine birds in the apostlebird. Both species arenon migratory and defend a territory during the breeding season. The size of the territory during the breeding season is around 20 ha, after the breeding season when the chicks arefledged the group may range over a larger territory. On the death of one of the dominant breeders the groups break up, and the remaining dominant bird will take immatures from their group and find a lone bird to form a new group.[2] The majority of recruits into any group after its establishment are youngsters from previous breeding seasons.[4] These helpers are important in breeding success, so much so that white-winged choughs have been reported to kidnap nearly fledged chicks from other groups in order to increase the size of the kidnapping group.[5]
As the common name of the family suggests, thenests are constructed out of mud. These bowl shaped nests take several days to construct, longer if supplies of mud dry up before the nest is finished. Nests are built opportunistically when rain causes muddy puddles, and may be reused if possible. Around three to five ovaleggs are laid in each clutch. These eggs areincubated for around twenty days by all members of the group, and feeding and brooding duties are also shared within the group.[2] This family has a very long period of fledgling care, with full independence from the parents and helpers taking up to 200 days.[6]