Spatially broad and long-term monitoring studies are lacking in tropical intertidal systems yet are necessary to test predictions regarding community assembly. To fill this gap, we examined spatial and decadal temporal patterns in benthic community structure at rocky intertidal sites along the main islands of Hawai'i. Quantitative community surveys done in 2017 across nine sites and five islands showed that organismal composition differed by site, substrate type, and island. Secondly, we leveraged an earlier dataset collected using the same methods and analyzed intertidal communities at five sites on three Hawaiian islands for temporal changes in organismal abundance and composition from 2006 and 2007 vs. 2016 and 2017. Overall community structure differed significantly across years and decades. Most decadal differences were site specific, such as the fivefold increase in turf algae at one site. Crustose coralline algae and Turbinaria ornata increased significantly across five sites; both are physically resilient algae and similar increases in their abundances have been observed in tropical systems worldwide. This increase in physically resilient macroalgal species is potentially caused by global drivers, such as rising temperatures and changing land uses. In conclusion, there is evidence that both local and regional factors contribute to structuring tropical intertidal communities.

Studying migration is critically important for understanding the full-annual cycle of migrating birds and aids in management and conservation. In recent years, global positioning system (GPS) and platform transmitting terminal (PTT) tags have become miniaturized, revolutionizing migration research by allowing for higher location accuracy and global coverage for smaller species. We reviewed 116 primary research papers from 2006 to 2021 that reported on GPS- or PTT-tagged small birds (<500 g) during migration and assessed research aims, tag efficacy, ecological findings, and future opportunities. Reviewed papers covered 58 unique species (nearly half of which were shorebirds) and 65% of studies tagged birds at breeding grounds. Tags that did not require retrieval had higher success obtaining data, with PTT tags having the greatest success (85% of deployed tags had data). Of studies that reported tag load information, most (70%) reported tag loads ≥3% body mass, which is a potential concern given that 3% is considered the preferable upper limit. Most papers (69%) focused on presenting spatial information such as migratory routes, stopover sites, and habitat use, and only 33% of papers tested explicit hypotheses, demonstrating that we are in the early stages of understanding small bird migration at fine scales. Almost all tag deployments (93%) occurred in the northern hemisphere, most often in the United States (24%), indicating a deficiency in GPS and PTT research on small bird migration from the southern hemisphere. GPS and PTT tags have revealed new biological insights not possible with other technologies by providing fine-scale movement data and global coverage. There are exciting opportunities for researchers to move beyond descriptive spatial studies and explore hypothesis-driven migratory research, into topics such as intraspecific variation, carry-over effects, and climate-driven movements for irruptive species.

Synopsis Pair-living is a common social system found across animal taxa, and the relationship between pair-living and reproduction varies greatly among species. Siphonaria gigas, hermaphroditic pulmonate gastropods, often live in pairs in the rocky intertidal zone of the tropical Eastern Pacific. Combining genetic parentage analysis using four polymorphic microsatellite loci with behavioral observations from a 10-week field study, we provide the first description of the mating system of a Siphonaria species incorporating genetic data. S. gigas mated both within-pair and extra-pair and three out of four paired S. gigas individuals produced egg masses with extra-pair paternity. Multiple paternity was detected, but at a relatively low frequency (19% of egg masses) compared to other marine gastropods. Behavioral data indicate one potential advantage of pair-living: paired S. gigas produced almost twice as many egg masses as their solitary counterparts over four reproductive cycles. These observations, together with constraints on the movement of S. gigas, suggest that pairing may ensure mate access and increase reproductive success.

Global sea surface temperatures (SSTs) are increasing, and in Hawaiʻi, rates of ocean warming are projected to double by the end of the 21st century. However, current nearshore warming trends and their possible impacts on intertidal communities are not well understood. This study represents the first investigation into the possible effects of rising SST on intertidal algal and invertebrate communities across the Main Hawaiian Islands (MHI). By utilizing citizen-science data coupled with high-resolution, daily SST satellite measurements from 12 intertidal sites across the MHI from 2004–2019, the response of intertidal algal and invertebrate abundance and community diversity to changes in SST was investigated across multiple spatial scales. Results show high rates of SST warming (0.40°C Decade-1) over this study’s timeframe, similar to predicted rates of warming for Hawaiʻi by the end of the 21st century. Changes in abundance and diversity in response to SST were variable among intertidal sites, but differences in antecedent SST among intertidal sites were significantly associated with community dissimilarity. In addition, a statistically significant positive relationship was found between SST and Simpson’s diversity index, and a significant relationship was also found between SST and the abundance of six dominant taxa. For five of these six dominant taxa, antecedent SSTs over the 6–12 months preceding sampling were the most influential for describing changes to abundance. The increase in community diversity in response to higher SSTs was best explained by temperatures in the 10 months preceding sampling, and the resultant decreased abundance of dominant turf algae. These results highlight rapidly warming nearshore SSTs in Hawaiʻi and the longer-term effects of antecedent SSTs as significant drivers of change within Hawaiian intertidal communities. Therefore, we suggest that future research and management should consider the possibility of lagging effects of antecedent SST on intertidal communities in Hawaiʻi and elsewhere.