Diana Hamilton

Mount Allison University · Department of Biology

Semipalmated Sandpipers (Calidris pusilla) are Arctic-breeding shorebirds that use staging sites in Atlantic Canada during their annual migration to South America. The Bay of Fundy has long been recognized as a critical staging site for migrating Semipalmated Sandpipers and supports a large prey base. The diet of adult sandpipers in the Bay is flex...

Semipalmated Sandpipers (Calidris pusilla) are Arctic-breeding shorebirds that use staging sites in Atlantic Canada during their southbound migration to South America. The upper Bay of Fundy is recognized as a critical staging area, but hundreds of smaller sites outside the Bay of Fundy also host staging Semipalmated Sandpipers and have received co...

Elucidating factors (“drivers”) that influence succession after disturbance can explain ecological phenomena, including why communities vary spatiotemporally. To gain insight on drivers related to habitat availability, species availability, and species performance during succession, we conducted two field experiments on infaunal communities in inte...

The Bay of Fundy, Canada is a critical staging area for Semipalmated Sandpipers ( Calidris pusilla ) during post-breeding migration. Recent range-wide population declines and changes in diet and migratory timing in the Bay of Fundy prompted a re-examination of staging ecology, including length of stay (last estimated in 1981), which is used in calc...

Semipalmated sandpipers are Arctic breeding shorebirds that migrate to South America during the non-breeding season. Little work has been done to understand the daily movements, foraging habits and metabolic state of this species on stationary nonbreeding grounds. Our work was conducted at the Banco dos Cajuais Western Hemisphere Shorebird Reserve...

Many long-distance migratory birds use habitats that are scattered across continents and confront hazards throughout the annual cycle that may be population-limiting. Identifying where and when populations spend their time is fundamental to effective management. We tracked 34 adult whimbrels ( Numenius phaeopus ) from two breeding populations (Mack...

The macrotidal Bay of Fundy, Canada hosts large expanses of tidal mudflats colonized by microphytobenthos biofilms, dominated by diatoms. Microphytobenthos biofilms mediate ecosystem functions of the mudflats, including serving as a food resource for organisms such as nematodes, crustaceans, polychaetes and globally significant shorebird population...

Each year hundreds of millions of birds cross the Atlantic Ocean during the peak of tropical cyclone activity. The extent and consequences of migrant-storm interactions remain unknown. We tracked whimbrels from two populations (Mackenzie Delta; Hudson Bay) to examine overlap between migration routes and storm activity and both the frequency and con...

Migrant shorebirds operate within a series of landscapes and must adjust their daily activities to achieve seasonal time and energy objectives. Night roosts are essential landscape elements that predators provide safety from predators for many shorebird species. What costs migrants incur to use night roosts and how these costs vary across staging s...

Infauna have an intimate relationship with the sediments they inhabit, and any study conducted upon infauna must, at the very least, describe sediment conditions. Common sediment assessments in intertidal systems include particle size distribution, as well as water and organic matter contents. These measures require extracting and processing a sedi...

The Bay of Fundy, Canada is a critical migratory stopover for Semipalmated Sandpipers (Calidris pusilla) during fall migration. Recent ecological changes combined with range-wide population declines indicate that a re-evaluation of habitat use and regional fidelity is required. The Bay of Fundy is divided into three regions, each of which contains...

Long-distance migrants are assumed to be more time-limited during the pre-breeding season compared to the post-breeding season. Although breeding-related time constraints may be absent post-breeding, additional factors such as predation risk could lead to time constraints that were previously underestimated. By using an automated radio telemetry sy...

Large numbers of Semipalmated Sandpipers (Calidris pusilla) use the Bay of Fundy, Canada, as a stopover site during their southbound migration from breeding to wintering grounds. The species exhibits a geographic cline in bill length on the breeding grounds (larger in east). Based on a previous analysis of morphometric traits that detected a small...

For most shorebird species, our understanding of the basic limiting factors and when or where they operate during the annual cycle is currently inadequate to either understand ongoing declines or effectively allocate conservation resources for recovery. Whimbrels (Numenius phaeopus) exhibit delayed recruitment and have low fecundity, and population...

Carcinus maenas (European Green Crab) is an invasive marine portunid crab that has established populations globally outside of its native range and has been implicated in declines of benthic invertebrates in invaded ecosystems. Observations of Green Crab on intertidal mudflats in the upper Bay of Fundy have increased in recent years. We assessed th...

The spillway gates of the Petitcodiac Causeway, a hydraulic structure ~35 km upstream of the mouth of the Petitcodiac River in New Brunswick, Canada, were permanently opened in April 2010. The short-term effect opening the spillway gates had on downstream intertidal mudflats of the upper Bay of Fundy was investigated. Specifically, a multivariate b...

Semipalmated Sandpipers (Calidris pusilla L., 1766) that migrate through the upper Bay of Fundy, Canada, depend on a rich food supply to fuel their continued migration. Although past studies have reported a diet dominated by the amphipod Corophium volutator (Pallas, 1766), an animal rich in n-3 polyunsaturated fatty acids (PUFAs), recent evidence s...

We compiled a >50-year record of morphometrics for semipalmated sandpipers (Calidris pusilla), a shorebird species with a Nearctic breeding distribution and intercontinental migration to South America. Our data included >57,000 individuals captured 1972–2015 at five breeding locations and three major stopover sites, plus 139 museum specimens collec...

We describe a new collaborative network, the Motus Wildlife Tracking System (Motus; https://motus.org), which is an international network of researchers using coordinated automated radio-telemetry arrays to study movements of small flying organisms including birds, bats, and insects, at local, regional, and hemispheric scales. Radio-telemetry has b...

The objective of this study was to determine the implications of extreme tidal events on duration of stay and behavior of Semipalmated Sandpipers (Calidris pusilla) during migratory stopover in Cobequid Bay, Nova Scotia. This area is part of the Bay of Fundy and experiences the largest tidal range in the world. Radiotelemetry was used to monitor du...

Molecular scatology and next-generation sequencing identified previously unknown linkages among ecosystems in the diet of Semipalmated Sandpipers (Calidris pusilla) in the Bay of Fundy, Canada. During their annual migratory stopover, sandpipers consumed a wider range of prey items than previously thought, suggesting that they are not selecting for...

Top-down, bottom-up, middle-out and abiotic factors are usually viewed as main forces structuring biological communities, although assessment of their relative importance, in a single study, is rarely done. We quantified, using multivariate methods, associations between abiotic and biotic (top-down, bottom-up and middle-out) variables and infaunal...

Map of study sites (i.e., intertidal mudflats) in the Bay of Fundy, Eastern Canada. (DOCX)

Preliminary PERMANOVAs conducted to determine if the smaller community dataset (n = 4 samples per transect dataset), which contained all biotic and abiotic variables, produced similar results to the full community dataset (n = 12 samples per transect), which did not contain all abiotic variables. (DOCX)

Non-metric multidimensional scaling (nMDS) plots of the infaunal community composition on eight intertidal mudflats (a.k.a. sites) in the upper Bay of Fundy, Canada, and eight sampling rounds per year over two years (2009–2011). (DOCX)

Bubble plots of the nMDS plots from S2 Fig, representing the magnitude of covariates (abiotic, top-down or bottom-up variables) that accounted for the highest proportion of the observed variation in the infaunal community. (DOCX)

Biotic and abiotic variables of the expansive intertidal mudflats of the upper Bay of Fundy, Canada, were examined at 8 geographically separate sites, regularly over 2 years (2009-2011). Invertebrate densities, surface densities of primary producers (mainly diatoms, measured as chlorophyll a concentration), shorebird and fish foraging activity, and...

As hypoxic conditions spread in our oceans, indices that quickly and efficiently assess oxygen content in sediment pore water, and habitat quality are increasingly becoming desirable. Depth to the apparent redox potential discontinuity (aRPD) in sediment is one such index; however, the relationship between aRPD depth and oxygen content is still unc...

Predator avoidance is an important component of predator-prey relationships and can affect prey availability for foraging animals. Each summer, the burrow-dwelling amphipod Corophium volutator is heavily preyed upon by Semipalmated Sandpipers (Calidris pusilla) on mudflats in the upper Bay of Fundy, Canada. We conducted three complementary studies...

Movement of animals on intertidal mudflats can have profound consequences for population and community dynamics. Such movement is often influenced by biotic interactions, but the abiotic environment can also be important, affecting the strength of species’ interactions and even changing their outcome. Here, we focused on two biotic interactions and...

Measurements of the redox potential discontinuity (RPD) are becoming progressively more important as they are considered a promising variable to evaluate the ecological status of many benthic environments. Two methods are commonly used to measure depth of the RPD in intertidal habitats: 1) visually, often by digital imaging (aRPD); or 2) with redox...

Knowledge of dispersal vectors used by organisms is essential to the understanding of population and community dynamics. We report on ice rafting, a vector by which intertidal benthic invertebrates can be transported well outside their normal dispersal range during winter in temperate climates. We found multiple invertebrate taxa in sediment-laden...

The outer Bay of Fundy, Canada, hosts rocky intertidal communities often dominated by beds of blue mussels Mytilus edulis, which support vertebrate and invertebrate predators at different times of the year. Strong predation by ducks in this system opens the possibility of a trophic cascade whereby ducks substantially reduce mussel density, opening...

Semipalmated Sandpipers (Calidris pusilla (L., 1766)) use the upper Bay of Fundy, Canada, as a critical stopover site during their annual fall migration to wintering grounds in South America. While in the area, they feed extensively on mudflat invertebrates. Historically the amphipod Corophium volutator (Pallas, 1766) has been thought to make up th...

Negatively correlated densities between two species can be attributed to effects on vital rates and/or movement. On intertidal mudflats in the upper Bay of Fundy, Canada, mechanisms underlying the negative correlation between the densities of two dominant macro-invertebrates, the mud snail Ilyanassa obsoleta and the burrow-dwelling amphipod Corophi...

We evaluated the potential for between-mudflat dispersal of individuals of the burrow-dwelling amphipod Corophium volutator. We first estimated the distances travelled by measuring vertical distribution of swimmers in the water column and their activity in relation to the tidal cycle. We found amphipods were located high over the substratum (up to...

During its fall migration stopover on mudflats in the upper Bay of Fundy, Canada, the Semipalmated Sandpiper (Calidris pusilla) is thought to feed primarily on the amphipod Corophium volutator (mudshrimp). Semipalmated Sandpipers typically use a peck-probe foraging strategy and, until recently, there had been little evidence of variability or oppor...

Blue mussels (Mytilus edulis) play an important role in many coastal marine communities, regulating biodiversity and serving as food for many predators. Interactions between predators mediate their impact on mussel prey, and thus have indirect effects on the mussel bed community. We studied the effects of predator density and species composition on...

We reared gypsy moth larvae outdoors under natural temperature and photoperiod regimes on red oak (Quercus rubra L.) and sugar maple (Acer saccharum Marsh). Initiation of the experiment coincident with the peak hatch of the local gypsy moth population assured normal synchrony between foliage quality and larval development. Compared with larvae rear...

Zebra mussels (Dreissena polymorpha) are subject to size-selective predation by several species of diving ducks and fish in Europe and North America. Ingested mussels are crushed, but the internal septum in the umbonal region of the mussel usually remains intact. Using mussels collected at Point Pelee, Lake Erie, I showed that there is a strong rel...

The upper Bay of Fundy is a critical staging area for migrating semipalmated sandpipers (Calidris pusilla), which feed extensively on the amphipod Corophium volutator. Recent changes in the distributions of birds around the bay have generated interest in understanding the factors that influence shorebirds' habitat use. To examine some of these fact...

Invertebrates in soft-bottom marine communities exhibit a range of responses to predators and competitors, including both emigration and avoidance. Corophium volutator (Pallas), a burrowing amphipod abundant in the upper Bay of Fundy, Canada, frequently interacts with the eastern mudsnail, Ilyanassa obsoleta (Say), as both species utilize similar h...

Blue mussels (Mytilus edulis) play important roles in many coastal marine communities, regulating biodiversity and acting as food for many predatory organisms. Predators of mussels are known to interact with each other via competition, stimulation, and adaptations to intraguild predation. These interactions mediate the impact of predators on their...

The scale of variation in population densities and other demographic variables is an important consideration in the design and interpretation of experiments and sampling programs. Here, we studied spatial and temporal variation in populations of Corophium volutator, an intertidal amphipod that is the most abundant macro-invertebrate on mudflats in...

This study quantifies the relative importance of factors affecting selection of brood-rearing areas by Common Eiders (Somateria mollissima) according to duckling age. A total of 1,431 h of observation was conducted from June-August on the New Brunswick mainland in 2000 and on Grand Manan Island in 2001. The number of breeding pairs of Great Black-b...

We investigated interactions between two dominant invertebrate species of intertidal soft-sediment environments of the northwest Atlantic, the mud snail Ilyanassa obsoleta and the burrowing amphipod Corophium volutator, on a mudflat of the upper Bay of Fundy, Canada. Distribution of I. obsoleta on the mudflat was highly patchy and negatively correl...

We conclude that the heat shock response is enhanced in juvenile compared with adult rainbow trout, Oncorhynchus mykiss. We have shown that the magnitude of the inducible heat shock response, as measured by increases in the heat shock protein (Hsp) Hsp70 is significantly greater in the hearts of fingerling than in adult trout following an acute (1h...

The upper Bay of Fundy is a critical stopover site for Semipalmated Sandpipers (Calidris pusilla) during their fall migration. However, little is known about factors that influence selection of feeding and roosting sites by these birds, or the extent to which birds move between different sites during their time in the region. Using radio-telemetry,...

Habitat heterogeneity often affects movement behaviours of animals, and consequently their spatial distribution. We evaluated the effect of immersion at low tide on the distribution, fine-scale movement patterns and daily movement patterns of the mud snail Ilyanassa obsoleta on a mudflat in the upper Bay of Fundy, Canada. Mud snails migrate onto in...

Predation of cultivated mussels by diving ducks can threaten the viability of mussel farms. Conventional scaring tactics have had limited success at deterring ducks from feeding on cultivated mussels, because of rapid habituation and 24-h feeding cycles of some waterfowl species. We tested a socking material containing a biodegradable protective la...

Mathematical models of commercially important species enable one to integrate the diversity of information on these species, understand mechanisms responsible for observed population dynamics, and assess management scenarios. We present a population model for blue mussels Mytilus edulis grown in suspended culture in 2 bays in Prince Edward Island,...

During their annual mid- to late-summer southward migration, Semipalmated Sandpipers (Calidris pusilla) feed intensively on the amphipod Corophium volutator on intertidal mudflats in the Bay of Fundy. Corophium, in turn, feed on diatoms and bacteria. Using a series of bird exclosures and fertilizer addition, we examined top-down and bottom-up effec...

In suspended aquaculture, the size of mussel seed and the density at which these mussels are placed in socks are two important factors affecting mussel production. However, the effect of these two factors has yet to be examined simultaneously. We conducted two large-scale field experiments to assess the effect of seed size and initial density on gr...

Mussels usually exhibit morphological variations in response to their environment. We conducted two field experiments in which we assessed the effect of mussel density and size on the morphology of blue mussels (Mytilus edulis) grown in suspended culture using longlines. Morphological measurements were taken over two and a half years on mussels rea...

Little is known about the effect of commercial rockweed (Ascophyllum nodosum) harvest on intertidal community structure, and on interactions among species. Using predator-exclusion cages and by simulating rockweed harvest, we studied the combined effects of predation by common eiders (Somateria mollissima) and harvest on an intertidal invertebrate...

Corophium volutator (Pallas), gammaridean amphipods found on intertidal mudflats, are frequently collected in mud samples sieved on mesh screens. However, mesh sizes used vary greatly among studies, raising the possibility that sampling methods bias results. The effect of using different mesh sizes on the resulting size-frequency distributions of C...

Common Eider (Somateria mollissima) ducklings and associated females in the Bay of Fundy feed extensively on invertebrates found in association with Knotted Wrack (Ascophyllum nodosum), commonly referred to as rockweed. To assess whether commercial harvest of rockweed, which is occurring in New Brunswick, might adversely affect ducklings, I examine...

Predation and disturbance have been well studied in intertidal communities. However, the impact of vertebrate predators, particularly waterfowl, has been only infrequently determined in long-term intertidal studies. Using predator exclusion cages and simulated abiotic disturbance, I studied the direct and indirect effects of predation by Common Eid...

Predation and disturbance have been well studied in intertidal communities. However, the impact of vertebrate predators, particularly waterfowl, has been only infrequently determined in long-term intertidal studies. Using predator exclusion cages and simulated abiotic disturbance, I studied the direct and indirect effects of predation by Common Eid...

We studied size-selective predation by Common Eiders (Somateria mollissima) feeding on blue mussels (Mytilus edulis). Selection varied with location, season, and prey availability, and for the most part ducks preferred smaller mussels than those that would have been the most energetically profitable on a per prey basis. We tested predictions from t...

Zebra mussels (Dreissena polymorpha) are a novel and abundant potential food source for several species of diving ducks in the Great Lakes region. Using predator exclusion cages, behavioral observations, and analyses of duck gizzard contents, we examined the predator-prey relationship between zebra mussels and their duck predators during the fall m...

Thesis (Ph. D.)--University of Guelph, 1998. Includes bibliographical references.