DOI: 10.5061/dryad.95x69p8pf
title: Data for: Polymorphism at the nestling stage and host-specific mimicry in an Australasian cuckoo-host arms race

description: Decades of research have shown that the coevolutionary arms race between
 avian brood parasites and their hosts can promote phenotypic
 diversification in hosts and brood parasites. However, relatively little
 is known about the role of brood parasitism in promoting phenotypic
 diversification of nestlings. We review field data collected over four
 decades in Australia, New Caledonia and New Zealand to assess potential
 for coevolutionary interactions between the shining bronze-cuckoo
 (Chalcites lucidus) and its hosts, and how diversification at the nestling
 stage may be generating different subspecies. The shining bronze-cuckoo is
 a specialist parasite of a few hosts in the family Acanthizidae. It has
 diversified into subspecies, of which the nestlings closely mimic the
 respective host nestlings in each region. Additionally, some cuckoo
 subspecies have polymorphic nestlings.  The Acanthizidae hosts
 have similar breeding and nesting habits and only moderately effective
 frontline defences against parasitism at cuckoo egg laying or at the egg
 stages. However, some hosts have developed highly effective defences at
 the nestling stage by recognising and ejecting cuckoo nestlings from the
 nest. As with the cuckoo nestlings, some hosts have polymorphic nestlings.
 The coevolutionary interactions in each region suggest different
 evolutionary stages of the arms race in which either the parasite or the
 host is currently in the lead. The presence of moderately effective
 defences at the egg laying and egg stages might explain why some hosts do
 not have defences at the nestling stage. The south-Pacific cuckoo – host
 systems are excellent models to explore the evolutionary mechanisms
 driving the diversification at the nestling stage in the coevolutionary
 arms race between avian brood parasites and their hosts.
description: We measured spectral reflectance (300-700 nm) from the skin of
 1-4 days old cuckoo and host nestlings in the field using portable
 spectrometers (AU and NZ; USB2000, Ocean Optics, Dunedin, FL, USA; NC:
 Jaz-EL-200, Ocean Optics, Dunedin, FL, USA) with illumination by pulsed
 xenon or deuterium-tungsten-halogen light sources. Before measurements, we
 calibrated the spectrometers with a diffuse reflectance standard (WS-1,
 Ocean Optics, Dunedin, FL, USA). We took 6 measurements from each nestling
 (2 from the hips, 2 from the shoulders and 2 from the head) and calculated
 an average spectrum for each individual.  We used the
 package pavo to import, process and analyse the spectral data in R 3.6.3.
 The shining bronze-cuckoo and its Acanthizidae hosts are predicted to have
 a violet-sensitive (VS) visual system, therefore we run a visual modelling
 analysis using the peafowl as a VS avian vision model. We run an
 additional analysis using an ultraviolet-sensitive (UV) avian vision model
 (blue tit). We used the function vismodel to calculate the quantum catches
 of the VS model with a D65 (standard daylight) irradiance spectrum. We
 used a log form of the receptor-noise limited (RNL) model of Vorobyev and
 Osorio (1998) to estimate noise at low light levels.
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