Research on neighbor-stranger discrimination theory has revealed the significance of social context and biological traits affecting the mechanisms that drive social discrimination, such as the dear ...enemy or nasty neighbor effects (strangers or neighbors more threatening, respectively). Nevertheless, the effects of territory size and human activity on neighbor-stranger experiments have yet to be explored. By examining behavioral responses to spontaneous duets of neighbors and playbacks of strangers’ duets, we tested whether rufous horneros (Furnarius rufus) in smaller territories show heightened aggression, responding more strongly to strangers and less to neighbors than those in larger territories. This could be expected because birds in larger territories might struggle to differentiate competitors due to limited interactions, hindering familiarity with neighbors. Meanwhile, birds in smaller territories are likely to treat neighbors as dear enemies due to the need to minimize territorial costs caused by presumed frequent intrusions or to protect limited resources. Contrary to predictions, rufous horneros responded more strongly to strangers than neighbors, regardless of owner territory sizes. This suggests that the presumed higher intruder frequency in smaller territories does not necessarily lead to adjusted dear enemy relationships. Yet, small territory holders exhibited heightened vocal responses to duets of unfamiliar intruders, indicating a stronger 'dear enemy' effect compared to birds with larger territories. We also tested whether dear enemy relationships would be heightened during weekends. This is linked to the difficulty urban birds might face in distinguishing neighbors from strangers during high human activity days (i.e., on weekdays), due to factors like noise masking intruder acoustic cues and heightened vigilance. Territorial owners exhibited consistent dear enemy behavior towards neighbors, regardless of our proxy for human activity. This underscores their ability in identifying competitor identities within urban settings.
•Urban horneros treat strangers more aggressively than neighbors (dear enemy effect).•The dear enemy effect is unaffected by territory size of the territorial owners.•The dear enemy effect holds regardless of a weekly cycle of human disturbance.
Bird migration within the Neotropics Jahn, Alex E.; Cueto, Víctor R.; Fontana, Carla S. ...
The Auk,
10/2020, Letnik:
137, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the ...last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozens of species that migrate latitudinally within South America, altitudinally within various mountain ranges, to and between Caribbean islands, and longitudinally across diverse ecosystems such as the Amazon rainforest. Advances in miniaturized tracking technologies, enormous citizen science databases, and powerful analytical approaches provide an unprecedented ability to detect and evaluate temporally and spatially fine-scale patterns, greatly facilitating the study of migratory patterns across tropical regions. We argue that a renewed effort in research on short- and long-distance bird migration within the Neotropics will allow (1) comparative studies that identify the emergent properties of migratory behavior, (2) identification of the convergent or unique mechanistic drivers of migration across diverse ecological settings, (3) formulation of effective conservation and management plans for migratory Neotropical birds, and (4) predictions about how migratory birds will respond to large-scale climatic changes within the Neotropics. Here, we review the current state of knowledge on Neotropical bird migration, with a focus on South America. We specifically examine similarities and differences in the observed migratory patterns of birds that breed in the Nearctic compared to the Neotropics and highlight key future research questions.
The K¯N system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series X-rays of kaonic hydrogen ...atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As X-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ϵ1s=−283±36(stat)±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy K¯N interaction.
The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 experiment, at the Laboratori Nazionali del Gran Sasso searches for X-rays from copper atomic transitions that are prohibited by the ...Pauli exclusion principle. Candidate direct violation events come from the transition of a 2p electron to the ground state that is already occupied by two electrons. From the first data taking campaign in 2016 of VIP-2 experiment, we determined a best upper limit of Formula omitted for the probability that such a violation exists. Significant improvement in the control of the experimental systematics was also achieved, although not explicitly reflected in the improved upper limit. By introducing a simultaneous spectral fit of the signal and background data in the analysis, we succeeded in taking into account systematic errors that could not be evaluated previously in this type of measurements.
The first observation of the kaonic 3He 3d→2p transition was made, using slow K− mesons stopped in a gaseous 3He target. The kaonic atom X-rays were detected with large-area silicon drift detectors ...using the timing information of the K+K− pairs of ϕ-meson decays produced by the DAΦNE e+e− collider. The strong interaction shift of the kaonic 3He 2p state was determined to be −2±2(stat)±4(syst) eV.
We present a new measurement of the Λ4H hypernuclear lifetime using in-flight K− + 4He → Λ4H + π0 reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection ...of the hypernuclear bound state using only the γ-ray energy decayed from π0. This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from (K−, π−) reaction. As the first application of this method, our result for the Λ4H lifetime, τ(HΛ4)=206±8(stat.)±12(syst.)ps, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton (Λ3H) using the same setup in the near future.
We measured a set of π±Σ∓, π0Σ0, and π−Σ0 invariant mass spectra below and above the K¯N mass threshold in K−-induced reactions on deuteron. The measured πΣ mass spectral shape is well reproduced via ...the two-step mechanism, i.e., a neutron knocked out at a forward angle from a deuteron by an incident K−, with the K¯ recoiled backward reacting with the residual nucleon to produce π and Σ. We deduced the S-wave K¯N→πΣ and K¯N→K¯N scattering amplitudes in the isospin 0 channel in the framework of a K¯N and πΣ coupled channel. We find that a resonance pole corresponding to Λ(1405) is located at 1417.7−7.4+6.0 (fitting errors)−1.0+1.1 (systematic errors) + −26.1−7.9+6.0 (fitting errors)−2.0+1.7 (systematic errors) i MeV/c2, closer to the K¯N mass threshold than the value determined by the Particle Data Group.
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