# Impacts of tropical cyclones on Northwest Atlantic seabirds: insights from a Category 1 hurricane

## TL;DR

This paper examines how Category 1 hurricanes impact seabird breeding in Newfoundland, using Hurricane Larry as a case study to show increased mortality and stranding events.

## Contribution

The study provides new insights into the specific impacts of tropical cyclones on seabird colonies in the Northwest Atlantic, particularly highlighting Hurricane Larry's effects.

## Key findings

- Northern Gannets and Leach’s Storm-Petrels experienced increased stranding and mortality during Hurricane Larry in 2021.
- Historical Category 1 hurricanes have overlapped with the breeding seasons of these seabirds in Newfoundland.
- Stranding and mortality rates during Hurricane Larry were higher than in surrounding years.

## Abstract

Tropical cyclones are annual occurrences in the western North Atlantic Ocean, where many seabird species are vulnerable to the environmental factors associated with extreme weather events. We summarize the history of tropical cyclones in Newfoundland, Canada, which hosts globally significant populations of seabirds. We examine the interactions that historical tropical cyclones have had with breeding seabirds by plotting the temporal association of Category 1 hurricanes with the breeding phenology of colonial seabirds in Newfoundland and identifying which major colonies have fallen within the pathways of these hurricanes. As a case study, we explore how Hurricane Larry (2021) coincided with increased stranding and mortality of Northern Gannets and Leach’s Storm-Petrels. The breeding seasons of Northern Gannets and Leach’s Storm-Petrels overlapped with all Category 1 hurricanes making landfall in Newfoundland from 1851 to 2024, whereby the central pathways of at least one hurricane passed over the six large Leach’s Storm-Petrel colonies and at least one of the Northern Gannet colonies. For Northern Gannets, a notable stranding and mortality event occurred with at least 146 stranded and 130 dead from September 13 to 24, 2021. For Leach’s Storm-Petrels, 19 birds were observed stranded and 16 died from September 10 to 14, 2021, which was higher than strandings and deaths reported during this period in 2020, 2022, 2023, and 2024. As global climate change drives shifts in the timing, frequency, severity, and attributes of tropical cyclones, we raise the concern that the impacts of tropical cyclones on breeding seabirds may worsen and lead to high mortality in some years.