Many animal species communicate with their mates through acoustic signals, but this communication seems to become a struggle in urbanized areas because of increasing anthropogenic noise levels. Several bird species have been reported to increase song frequency by which they reduce the masking impact of spectrally overlapping noise. However, it remains unclear whether such behavioral flexibility provides a sufficient solution to noisy urban conditions or whether there are hidden costs. Species may rely on low frequencies to attract and impress females, and the use of high frequencies may, therefore, come at the cost of reduced attractiveness. We studied the potential tradeoff between signal strength and signal detection in a successful urban bird species, the great tit (Parus major). We show that the use of low-frequency songs by males is related to female fertility as well as sexual fidelity. We experimentally show that urban noise conditions impair male-female communication and that signal efficiency depends on song frequency in the presence of noise. Our data reveal a response advantage for high-frequency songs during sexual signaling in noisy conditions, whereas low-frequency songs are likely to be preferred. These data are critical for our understanding of the impact of anthropogenic noise on wild-ranging birds, because they provide evidence for low-frequency songs being linked to reproductive success and to be affected by noise-dependent signal efficiency. signal evolution | noise pollution | frequency-dependent masking | extra-pair paternity | signal trade-off

We present the first multigene phylogeny focused on Eristalinae (Diptera: Syrphidae) utilizing a dataset containing 120 flower fly species from across all four subfamilies and representing 13 out of 16 tribes. Eight genes were used in the construction of the phylogeny: mitochondrial cytochrome c oxidase subunit I and the nuclear genes 28S ribosomal DNA, Alanylt RNA Synthetase, the carbamoyl phosphate synthase domain of CAD, Period, RNA-binding Protein 15 (RBP–15, 5’), Casein Kinase 1 and TULP for a total of ~6.7 kB of data. Eristalinae is recovered as paraphyletic with strong support for the elevation of Cerioidini, Merodontini and Volucellini to subfamilial status. Deineches, Flukea and Malometasternum render Criorhinina paraphyletic with respect to the type genus Criorhina. A clade with Criorhina, Matsumyia and Sphecomyia is strongly supported. The generic concept of Criorhina is paraphyletic, while Sphecomyia is monophyletic and Matsumyia is monophyletic but requires expansion. Evidence supports the resurrection of Romaleosyrphus and the creation of new genera. Criorhinina (stat. rev.) is restricted to contain Criorhina, Matsumyia, Romaleosyrphus and Sphecomyia. Thirteen changes to the higher classification of Syrphidae are proposed.

Summary1. Anthropogenic noise can affect intra-pair communication and therefore interfere with reproductive success. However, many animals have various signal strategies to cope with noise, although it is unclear whether they rely on direct auditory feedback from their own perception of noise or signal-to-noise level or on indirect social feedback from receivers. 2. We studied the role of social feedback on male great tit (Parus major) song adjustment by exclusively exposing females to artificial traffic noise inside their nest box. 3. We found a delay in female response latencies to male song in the noisy condition compared to the control condition on the first day of noise exposure. Males from the noise treatment group, not directly exposed to noise themselves, sang closer to the nest box within 3 days after the start of exposure. 4. The male's closer proximity to the nest box most likely led to the observed higher song amplitudes at the noisy nest boxes compared to quiet control nest boxes, and explains why the inside signal-to-noise ratios were restored to equal levels between treatment and control nest boxes after several days of exposure. 5. The initial difference between treatment groups in female response latencies at the start of exposure also disappeared accordingly. 6. Our results strongly suggest an active role for female birds in steering male song behaviour under noisy conditions. Males did not receive direct exposure during intra-pair communication, but adjusted their behaviour in the predicted direction. These data are important to understand the mechanisms related to communication in noise and reveal the critical role of ecology in shaping animal interactions.

A checklist of the Syrphidae species of the Republic of Georgia is presented. New hover fly (Diptera: Syrphidae) records from Georgia are provided as a result of field work conducted in 2018. At the same time, published syrphid records for the country are here reviewed and updated. A total of 357 species of hoverflies are now documented from Georgia, 40 of which are reported for the first time. Moreover, DNA barcodes were sequenced for 238 specimens, representing 74 species from this country.

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