Dollarbird – family group and feeding juveniles

posted in: Feeding-invertebrates | 0

“I had an opportunity to watch a family of Dollarbirds (Eurystomus orientalis orientalis) this morning from 7.15 to 9.00am. They comprised an adult and two juveniles. We were unfortunately interrupted by workmen who came in lorries to dig at the foot of the tree these birds were using. The juveniles were largely ‘kept’ 10-11 meters up in a Tabebuia pentaphylla (Tabebuia rosea) tree while the parent brought prey.

Adult with prey.

My first concern was the Lack of an Adult Partner
“These local Dollarbirds are well known to me as they I see them as a pair of adults intermittently near my home. I was surprised not to see another adult with the group as these birds are known to be monogamous (see HBW 2019) and I have seen them work together, fiercely defensive of nests. Most sources state that young birds are also cared for by both parents (see Wells 1999). I consider a number of possibilities as to why there was only one adult present to feed the juveniles:

Adult with prey.

1. The other adult was not supportive – this goes against available past observation of behaviour and literature records.
2. The other adult may have been injured or died.
3. Locally the clutch size is quoted as 2 eggs (Wells 1999). But other sources quote 2-4 (Robson 2002) or 2-5 eggs (HBW 2019). If this applies locally then it is possible that the other adult is looking after more juveniles.
4. Finally I considered if they had started breeding again. The two juveniles I saw were fairly mature and were able to forage for themselves occasionally. Could the pair have started a new batch of young (incubating eggs)? After all nesting holes in urban setting are at a premium (may want to protect their nesting hole).

Adult feeding juvenile.

Information on Prey brought to Juveniles
“I saw numerous feeding episodes (above shows adult feeding juvenile). The adult was already actively feeding the juveniles by the time I had arrived. Prey was obtained every 2-5 minutes. All prey was caught by aerial sallies. I did not see any prey taken from the ground. The adult bird has sharp vision and can spot prey 30-50 meters away (the common distance prey was obtained from), which is immediately acquired. Prey was brought back to the site where juveniles were located and a few sharp beak actions were done before feeding the juvenile. Almost no branch swiping to prepare prey was done (I saw one occasion where a prey was knocked on a branch once). All prey obtained during my observation period were large flying insects, many of the same species (see below, composite of a few visual records). Light was still low when I first observed feeding and I suspect this aids the parent, as beetles and some other flying insects are more active then. From what I could see a number were leaf beetle (Chrysomelidae).

Composite of a few visual records of prey caught.

Social Interaction in the Family Group and with Others
“One of the juveniles was fed more than the other. I suspect because the other could self-forage a little better. There was no sibling competition. On one occasion a Black-naped Oriole (Oriolus chinensis maculatus), also resident in the area, did an aggressive fly-by but was ignored by the parents. I have previously observed Black-naped Orioles chase away Dollarbirds from a perch.

Information on Calls by Adult and Juveniles
“I heard and recorded a number of calls and observed their relationship to family interactions and will post them once processed.”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
8th March 2019

Location: Ipoh, Perak, Malaysia
Habitat: Urban environment

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