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Determining space use for species is fundamental to understanding their ecology, and tracking animals can reveal insights into their spatial ecology on home ranges and territories. Recent technological advances have led to GPS-tracking devices light enough for birds as small as ~30 g, creating novel opportunities to remotely monitor fine-scale movements and space use for these smaller species. We tested whether miniaturized GPS tags can allow us to understand space use of migratory birds away from their capture sites and sought to understand both pre-breeding space use as well as territory and habitat use on the breeding grounds. We used GPS tags to characterize home ranges on the breeding grounds for a migratory songbird with limited available breeding information, the Golden-crowned Sparrow (Zonotrichia atricapilla). Using GPS points from 23 individuals across 26 tags (three birds tagged twice), we found home ranges in Alaska and British Columbia were on average 44.1 ha (95% kernel density estimate). In addition, estimates of territory sizes based on field observations (mean 2.1 ha, 95% minimum convex polygon [MCP]) were three times smaller than 95% MCPs created using GPS tags (mean 6.5 ha). Home ranges included a variety of land cover classes, with shrubland particularly dominant (64–100% of home range cover for all but one bird). Three birds tracked twice returned to the same breeding area each year, supporting high breeding site fidelity for this species. We found reverse spring migration for five birds that flew up to 154 km past breeding destinations before returning. GPS-tracking technology allowed for critical ecological insights into this migratory species that breeds in very remote locations. 

The dark-eyed junco (Junco hyemalis) has experienced rapid phenotypic diversification within the last 18,000 years, resulting in several subspecies that reside in partially overlapping regions across North America. These subspecies have distinct plumage and morphology. If members of a subspecies disproportionately mate with one another, we would expect genetic differences to accumulate between the subspecies. In parallel, their learned songs could also accumulate changes. If song is used by individuals to recognize members of their own subspecies during mate selection, which would prevent the production of less fit hybrid offspring between subspecies, then song differences might co-localize with subspecies boundaries. Here, we quantify 10 song features to explore subspecies-level song variation using song recordings from community-science databases. We build a machine learning classifier to measure how accurately the subspecies’ songs can be distinguished from one another. Here, we show that songs of dark-eyed junco subspecies exhibit significant song-feature differences. However, these differences do not necessarily lead to distinguishability between subspecies. Notably, we find that subspecies pairs with adjacent ranges that do not hybridize have much more distinguishable songs, and also more evidence for genetic differentiation, than pairs that are known to hybridize. Thus, song distinguishability appears to have predictive power about which subspecies will hybridize, suggesting that song might play a role in reinforcing certain subspecies boundaries more than others. Finally, we analyze subspecies-level song differences alongside available genetic data and geographic coordinates to characterize the current evolutionary landscape of the dark-eyed junco subspecies complex. We observe geographic signal in the song and genetic data, indicating that individuals who share a range are more likely to share song characteristics and be genetically similar. This study illuminates the existence of subspecies-level song differences in the dark-eyed junco and provides further clarity on the role learned song plays in reinforcing reproductive boundaries between dark-eyed junco subspecies. 

Abstract Different types of incoherent scatter radar (ISR) echoes are observed associated with aurora, including some which have been interpreted as signatures of cavitating Langmuir turbulence (CLT). Akbari et al. (2013)https://doi.org/10.1002/jgra.50314discussed two instances of correlation between CLT and naturally occurring radio emissions called medium frequency burst (MFB) which occur at substorm onsets. Based on that observation, radio detections of MFB from Toolik Lake Observatory have been applied to investigate occurrence of CLT in ISR data from Poker Flat Incoherent Scatter Radar and their possible correlation with MFB. Of 131 MFB events, 25 occurred within 15 min of an ISR echo detection, compared to 6 of 116 intervals of a control set with similar local time and seasonal distribution. The difference is significant at the 10⁻⁴level, suggesting that ISR echoes are more probable during substorm onset times identified using MFB as a proxy. However, only four observed ISR echoes coincident with one MFB event showed both specific characteristics consistent with CLT. Furthermore, investigation of the angle of arrival of MFB suggests that the electromagnetic emissions do not originate from the plasma volume where the ISR detects the echoes. The small number of coincident ISR echoes and MFB is expected due to the different volumes in which the emissions and the echoes are detected. 50% of the MFB events occurred within 20 min of a substorm onset independently identified versus 8% of the control set intervals, confirming the correlation of MFB with substorm onsets.