A study of various morphs of Changeable Hawk- eagles and their resultant offsprings
A Nature photographer Ms Cheryl Toh, shared with me 2 photos of a dark morph juvenile Changeable Hawk-eagle (Nisaetus cirrhatus).
According to Cheryl, both adult eagles were dark morphs resulting in the single offspring which was a dark morph. This nesting was observed in 2024 at Seletar area.
This was the first time that I have seen an image of a dark morph juvenile. All my encounters in the field were pale morph juveniles. This information from Cheryl Toh makes an interesting study of the offsprings of Changeable Hawk-eagles (CHE) with various combinations of pale and dark morph adults.
In the BESG article, `Changeable Hawk eagle: Pale x dark morph’, there were various combinations of adult eagle morphs discussed. They were documented by Mark Chan, Johnny Wee and Chan Yoke Meng. See Link: https://besgroup.org/2007/10/07/changeable-hawk-eagle-pale-x-dark-morph/
In 2006, Mark Chan documented a pair of 2 Pale morph adults nesting, resulting in a pale morph juvenile. Cheryl Toh also shared a photo of a pale morph juvenile from this similar adult combination, taken in 2024 at Yishun, see photo 3.
In 2007, Johnny Wee and Chan Yoke Meng documented a combination of 1 pale morph and 1 dark morph adults nesting, resulting in a dark morph juvenile.
In 2018, I documented a CHE nesting at Kranji Marsh where I saw 1 dark morph adult (blind in one eye) with a pale morph juvenile in a nest, see photo 4. In this case I assumed the other adult was a pale morph.
I have seen this combination before where a male dark morph mated with a female pale morph at Mt Faber Nature Park in 2023, see photo 5.
Perhaps its easier to visualize these combinations of adults and offsprings in a table form.
This study does invite some questions. Besides the 4 combinations shown in the table above, I wonder if there are possibilities for other combinations, such as Pale + Pale resulting in a dark morph juvenile and vice versa? From the table above, I wonder which is the most common and least common combinations of adults in Singapore. I also wonder regarding the combination of a pair of adult pale and dark morph eagles, what is the main factor that determines the colour of the juvenile?
The most common morph of CHE juveniles in Singapore that I have observed is the pale morph. I have never seen a dark morph juvenile before and therefore, the inputs from Cheryl Toh, Johnny Wee and Chan Yoke Meng are interesting to note.
Thong Chow Ngian
Contribution by Chng Eng Keong on 25 November 2024.
Dear authors and “citizen scientists”, great compilation. Thank you.
Our observations:
2022: Dover Forest East – Male Dark Morph and Female Pale Morph with Pale Morph eaglet.
2023: Dover Forest East – same (guess) Male Dark Morph and Female Pale Morph again with Pale Morph eaglet (the last eaglet of Dover Forest East).
2024 – no breeding as Forest is redeveloped and nest destroyed.
One Response
Dear authors and “citizen scientists”, great compilation. Thank you.
Our observations:
2022: Dover Forest East – Male Dark Morph and Female Pale Morph with Pale Morph eaglet.
2023: Dover Forest East – same (guess) Male Dark Morph and Female Pale Morph again with Pale Morph eaglet (the last eaglet of Dover Forest East).
2024 – no breeding as Forest is redeveloped and nest destroyed.