Natures wonders: drongos spot cuckoo eggs (Introduction)

by David Turell , Wednesday, July 26, 2023, 15:46 (484 days ago) @ David Turell

94% of the time:

https://www.science.org/content/article/two-these-eggs-are-impostors-can-you-spot-them?...

"The African cuckoo (Cuculus gularis) is infamous in the bird world. Mothers of this common parasitic species lay their eggs in the nests of a variety of other birds, camouflaging them so they can dupe unsuspecting moms into raising their hatchlings.

"But the fork-tailed drongo (Dicrurus adsimilis)—a glossy, red-eyed bird native to southern Africa—isn’t so easily fooled. According to a study published today in the Proceedings of the Royal Academy B, drongo moms can spot the counterfeits with 94% accuracy, despite cuckoo eggs being an almost perfect visual match for their own.

"The secret to the drongos’ success? Homing in on subtle variations in color and speckled patterning on the surface of their highly diverse eggs. Each female has a unique egg type, helping her spot impostors with accuracy that outstrips both humans and computer models."

From the original study:

https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1125

"We show, using a combination of image analysis, field experiments and simulations, that: egg colour and pattern mimicry of fork-tailed drongo eggs by African cuckoos is near-perfect on average; drongos show fine-tuned rejection of foreign eggs, exploiting unpredictable pattern differences between parasitic eggs and their own; and the high degree of interclutch variation (polymorphic egg ‘signatures’) exhibited by drongos gives them the upper hand in the arms race, with 93.7% of cuckoo eggs predicted to be rejected, despite cuckoos mimicking the full range of drongo egg phenotypes. These results demonstrate that model diversification is a highly effective defence against mimics, even when mimicry is highly accurate."

Comment: one should know one's own egg.