Ralph D. Morris

Sexual size dimorphism and assortative mating in the Brown Noddy

We report the results of a biometric study of adult Brown Noddies (Anous stolidus) nesting within the Culebra National Wildlife Refuge, Puerto Rico in 1985-1988. The body mass of adults varied significantly between years, but linear measurements did not. Males were significantly larger than females in all body measurements. This difference also was reflected within pairs. A discriminant function using head-bill and wing length successfully predicted the sex of 90% of birds. Measurements of male and female partners indicated that they were not paired at random with respect to body mass and showed positive assortative mating for this character. The causes and consequences of this relationship are discussed.

Patterns of adoption in ring-billed gulls: who is really winning the inter-generational conflict?

Abstract Although at variance with Darwinian theory, adoption of unrelated offspring has been reported in a variety of ground-nesting colonial seabirds. Pierotti & Murphy (1987, Anim. Behav. , 35, 435-444) suggest that an inter-generational conflict exists between disadvantaged chicks and unrelated adults, a conflict that often results in wandering chicks successfully soliciting investment from foster parents. Of 47 ring-billed gull, Larus delawarensis , chicks that departed their natal broods over four summers of field work, 34 remained in recipient broods for 3 or more days and received parental care (i.e. were successfully adopted), and 13 remained in recipient broods for less than 3 days (‘runners’). Chicks in broods that were subsequently subject to abandonment were fed at a significantly lower rate (on a per chick basis) than chicks in control broods (which neither adopted nor had a chick depart) or broods that subsequently adopted a chick. In most cases, adoptees were older than the oldest resident chick in the accepting brood, but runners were younger than resident chicks. Pairs whose oldest chick was less than 7 days were more likely to adopt foreign offspring than pairs with older chicks. Twenty-six (76%) of the 34 adopted chicks survived to at least 24 days (fledged). Pairs that adopted a chick realized a lower annual breeding success (chicks fledged/pair) than control pairs or pairs that had a chick depart their brood. Disadvantaged chicks that gain permanent acceptance into foreign broods ‘win’ the inter-generational conflict at the expense of the foster parents.

FROM TRAGEDY TO TRIUMPH: RENESTING IN RING-BILLED GULLS

ABsTAcT.-When animals that provide parental care to offspring are faced with actual or potential failure during a breeding bout, the option to continue breeding is countered by the option to cut losses and forego reproduction until the next breeding season. In 1990, we recorded laying date and laying order of eggs in 51 Ring-billed Gull (Larus delawarensis) clutches prior to their total loss by flooding. Pairs remained on territory and produced new clutches following a refractory period of 11.6 ? SD of 1.9 days. Post-loss clutches were initiated synchronously (n = 51 clutches in four days; 89% of all clutches marked in the 7 x 7 m study plot) but mostly contained significantly fewer and lighter eggs than first clutches. We contrast incubation, hatching and chick survival patterns of these storm-delayed pairs in 1990 with patterns of early-, peak- and late-nesting pairs at the same colony in 1992. The incubation and within-clutch hatching patterns of post-loss clutches 1990 were most similar to those of late nesting pairs in 1992, yet these storm-delayed pairs realized a fledging success similar to that of early-and peak-nesting pairs in 1992. We discuss larid reproductive strategies in the context of conditions that favor successful renesting. Received 22 August 1994, accepted 27 January 1995.

DIRECT AND INDIRECT CONSEQUENCES OF MINK PRESENCE IN A COMMON TERN COLONY

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Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

ABSTRACT Canadian and US federal wildlife agencies completed three surveys (1976–1980, 1989–1991, and 1997–2000) to census colonial waterbirds breeding on the Great Lakes. We here summarize and comment on nest numbers and colony site distribution of common terns (Sterna hirundo) and Caspian terns (Hydroprogne caspia). Common terns are in serious trouble on the Great Lakes. Numbers declined with substantial losses in nests (-19.1%) and colony sites (-23.2%) between the first and third censuses. An increase in numbers at US sites (+ 26.6%) did not compensate for losses (-33.1%) at Canadian sites. Caspian terns increased in nest numbers (+ 65.9%) and colony sites (+ 50.0%) over the same period. The increase at US sites (136.5%) was greater than at Canadian sites (11.5%). Most (70.7%, n = 186) common tern sites had nests during only one census; 17 sites (6.5%) had nests during all censuses. In contrast, 9 of 33 (27.2%) Caspian tern sites had nests during all censuses and contained a majority of nests (50–82%) in each census. Pairs of both species nested on natural substrates across the Great Lakes. Common terns nested mostly on artificial (human-constructed) substrates on the lower Great Lakes. We identify site characteristics that may have contributed to long-term (three census) occupancy by common terns (small size, artificial substrates, absence of ring-billed gulls) and Caspian terns (natural substrates on large, remote islands). We suggest an urgent need for protection and conservation of common tern colonies and identify specific priority sites for implementation of management protocols.

A new procedure for transmitter attachment : effects on brood attendance and chick feeding rates by male common terns

A transmitter crystal and battery were covered with epoxy and wired to a size 2 USFWS aluminum leg band. The male partners of 10 Common Tern (Sterna hirundo) pairs were captured during late incubation at a Port Colbome, Ontario tern colony and the transmitter units fixed to their legs. The total package weighed an average 1.08 g more than the usual mass of a single band. The brood attendance patterns and feeding frequency rates of transmittered-males and of their female partners were contrasted over a 20-day period with those of non-transmittered males and their partners. No differences were found. Advantages of the attachment procedure are speed of attachment, light mass, rapid loss of antennae following battery exhaustion, and lack of adverse effect on parental behavior.

Distribution and Abundance of Nesting Pairs of Herring Gulls (Larus argentatus) on the North American Great Lakes, 1976 to 2000

During the past three decades, Canadian and U.S. federal wildlife agencies completed three major surveys (1976–1980; 1989–1990; 1998–2000) to census seven species of colonially nesting waterbirds breeding on the Great Lakes. We summarize and comment on distribution and abundance of herring gulls (Larus argentatus), the most widely distributed of the species. Lake Huron consistently supported the highest number of nesting pairs, followed by Lakes Superior, Michigan, Erie, and Ontario. The pattern on four lakes was an increase in numbers between the first and second censuses, then a decrease between the second and third census. Numbers on Lake Huron declined between each census. Patterns may be food based although corroborative data are lacking. At colonies censused in all periods (1,025 sites representing 80–89% of all pairs counted), the population increased from 63,618 to 69,975 pairs (first to second census), then declined to 59,590 pairs (last census). The low average annual rate of change (–0.3%) indicates that the Great Lakes herring gull population was stable over three decades at around 60,000 breeding pairs. We identify 20 sites across the Great Lakes where large changes (> 50% between two successive periods) were recorded, and suggest that inter-colony movements could explain changes in numbers among 11 of these sites on Lakes Huron and Michigan. We offer two examples of research protocols that use annual data collection from a limited number of colony sites to more directly address the causes of numerical and distributional changes in numbers of nesting pairs.

Population Trends of Ring-billed Gulls Breeding on the North American Great Lakes, 1976 to 2009

Abstract. After near extirpation in the early 20th century, Ring-billed Gulls (Larus delawarensis) are currently (2009) the most abundant colonial waterbird nesting on the Great Lakes. Nest count data are reported from four decadal censuses (1976–2009) conducted by the Canadian Wildlife Service and the U.S. Fish and Wildlife Service. Numbers increased from 305,790 nests (1976–80) to a peak of 718,887 nests (1989–90), then decreased to 652,664 (1997–2000) and to 585,984 nests (2007–09). Changes varied spatially after the second census with greatest losses (-38.6%) at North Channel, Georgian Bay and northern Lake Huron colonies, and greatest gains (+324.2%) at Lake Michigan colonies. A total of 472 sites had nests in at least one census (Canada N = 319; U.S. N = 153). Eighteen (3.8%) colonies had >2,000 nests in all four censuses, and had 37.5–41.9% of all nests in each census. Site occupancy was fluid. A high proportion (56.8%, N = 268) of sites contained nests in only one of the four censuses, and few (N = 40, 8.5%) had nests in all censuses. Thirty-nine sites had >2,000 nests gains/losses between census periods; 14 (35.9%) were on urban/industrial lands with artificial substrates. Human management and predator activities at some colonies contributed to declines in nest numbers at these locations. Movement of breeding birds among colonies and changes in local food supply may have influenced changes in nest numbers elsewhere. Reasons for the overall nest losses across the Great Lakes after the second census are unknown.

Brown Noddies on Cayo Noroeste, Culebra, Puerto Rico : what happened in 1990 ?

1990 was atypical in several respects. Only 68% of adults alive in 1989 returned to breed in 1990, compared to about 90% in other years. In addition, adults were delayed in their diurnal occupation of the colony and in egg laying in 1990. Eggs laid in 1990 were the smallest of any year. However, head-bill length, body mass, and condition index of breeding birds that returned in 1990 were within the normal annual variation established for earlier years. None of the noddies that failed to return in 1990 has been seen through June 1993, and we suggest that they died, most likely as a result of Hurricane Hugo as it passed through the area in mid-September 1989. Despite the loss of a significant proportion of adults from the colony in 1990, the number of breeding pairs did not dramatically decline in that year, which suggests that a pool of young or inexperienced birds was available to recruit into the breeding population. The loss of regular breeders thus had the effect of reducing the average age or breeding experience in the colony, and also increasing the number of new pair bonds. These changes were the likely cause of late breeding and small egg size observed in 1990, and indicate the importance of a stochastic event such as Hugo on the population biology of a tropical seabird. Received 29 July 1993, accepted 21 November 1993.

A treatment for prevention of hatching in field-incubated ring-billed gull eggs

Numbers of ring-billed gulls (Larus delawarensis) have increased on the Great Lakes and upper St. Lawrence River since 1974, and reduction in the size of some colonies may be justified for nuisance control or safety reasons. One management procedure is to prevent the hatching of eggs without desertion of the clutch by adults. Our objective was to test the extent of hatching suppression induced by several chemical treatments on (1) fertile, domestic chicken eggs in laboratory incubators, and (2) ring-billed gull eggs in the field. Hatchability of chicken eggs was significantly reduced (P 6 weeks beyond the expected hatching time. Higher rates of preening and readjustment of nesting material were noted among adults incubating treated clutches compared to control adults. However, none of the experimental pairs deserted their clutches or renested in the breeding season of study. J. WILDL. MANAGE. 54(1):124-130 Ring-billed gull populations have increased in the Great Lakes and upper St. Lawrence River since the early 1970s (Ludwig 1974, Blokpoel and Tessier 1986), and inland nesting has recently been recorded (Blokpoel and Tessier 1984). Because of their generalist diet and tolerance of human activity, increased numbers of gulls usually increase the frequency of gull-human interactions which may lead to their classification as pest species. Contrary claims about the magnitude and significance of ring-billed gull-human interactions and the need for gull con rol procedures have recently been discussed (Blokpoel and Tessier 1988, Southern 1988). Populations of other species of Larus gulls have increased elsewhere (Drury and Nisbet 1969, Thomas 1972, Chabryzyk and Coulson 1976, Duncan 1978). In several such cases, gulls 1 Present address: Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada. This content downloaded from 157.55.39.35 on Fri, 02 Sep 2016 05:39:06 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 54(1):1990 PREVENTION OF HATCHING * Morris and Siderius 125 Table 1. The fate of fertile chicken eggs treated with 2 applications of the treatment chemical (S) and 1 application with water (W) at intervals of 0, 7, and 14 days after the start of incubation. Incubation and spray treatment were completed in the laboratory in March and April 1985. Each treatment group contained 24 eggs. Sodium silicate and sodium metasilicate were 75% solutions in water; dormant oil and dormant oil/DMSO were 65% solutions in water.