No change in common cuckooCuculus canorusparasitism and great reed warblers’Acrocephalus arundinaceusegg rejection after seven decades

Abstract

The coevolutionary process among avian brood parasites and their hosts involves stepwise changes induced by the antagonistic selection pressures of one on the other. As long‐term data on an evolutionary scale is almost impossible to obtain, most studies can only show snapshots of such processes. Information on host behaviour, such as changes in egg rejection rates and the methods of rejection are scarce. In Hungary there is an interesting case between the common cuckoo Cuculus canorus and the great reed warbler Acrocephalus arundinaceus, where the level of parasitism is unusually high (around 50%). We compared host rejection rates and methods of rejection from within our own project to that of an early study carried out and published almost 70 yr ago in the same region. Our comparisons revealed high and stable rates of parasitism (range: 52–64%), and marked fluctuations in the ratio of multiply parasitized nests (range: 24–52%). No difference was revealed in egg rejection rates after 7 decades (34–39%). Linear mixed‐effects modelling revealed no year effect on the type host responses toward the parasitic egg(s) during the years of study (categorized as acceptance, ejection, burial, and nest desertion). Cuckoo egg rejection was primarily affected by the type of parasitism, as more cuckoo eggs were rejected during single parasitism than from multiply parasitized nests. Our comparison did not reveal any directional changes in this cuckoo–host relationship, except a slight decrease in the frequency of multiple parasitism, which is likely to be independent from coevolutionary processes.

Can common cuckoos discriminate between neighbours and strangers by their calls?

“…50%; Moskát 143 & Honza, 2002;Zölei et al, 2015). Great reed warblers breed in reed beds grown on both sides 144 of small channels.…”

Egg spotting pattern in common cuckoos and their great reed warbler hosts: a century perspective

“…As we defined mimicry as the difference between host and parasitic eggs, this suggests that 268 mimicry was improving with time. Interestingly, a recent study on cuckoos and great reed warblers in Hungary pointed to the 286 stability of this host-brood parasitic relationship regarding parasitism rate and hosts' responses 287 to parasitism in the last 70 years (Zölei et al, 2015). In the present study, most variables 288 showed no difference between species, with the exception of coverage and total energy.…”

“…The study by Zölei et al (2015) also 300 suggests that despite the unusually and permanently high parasitism rate found in our study 301 area for at least the last 70-80 years, our host-brood parasite system is in dynamic 302 evolutionary equilibrium, where the ratio of hosts accepting or rejecting parasitic eggs is in 303 equilibrium (Lotem & Nakamura, 1998), and the recognition error rate is low (Stokke et al …”

“…Although we do not know exactly when this parasitic relationship started, our host-297 brood parasite system seems to be a relatively well-stabilized one as the main characteristics, 298 such as high parasitism rate, high rate of multiple parasitism, and mid-level rejection rate, 299 1 0 seem to be consistent over time (see Zölei et al, 2015). The study by Zölei et al (2015) also 300 suggests that despite the unusually and permanently high parasitism rate found in our study 301 area for at least the last 70-80 years, our host-brood parasite system is in dynamic 302 evolutionary equilibrium, where the ratio of hosts accepting or rejecting parasitic eggs is in 303 equilibrium (Lotem & Nakamura, 1998), and the recognition error rate is low (Stokke et al …”

“…Southern, 1954; Davies & Brooke, 1991; 83 Moksnes & Røskaft, 1995). The high cuckoo parasitism on great reed warblers has been 84 documented in detail from the Hungarian population (Zölei, Bán & Moskát, 2015), with eggs 85 collected from the early 1900's available for study in museums, offering an exceptional 86 possibility for revealing how cuckoo egg mimicry has changed over a more than 100-year 87 period. Here, we used digital images of the eggs of cuckoos and great reed warblers to 88 evaluate how the pattern of spottiness, as an important component of egg mimicry (Stoddard 89 & Stevens, 2010), changed from the 1900's until the present day.…”