N. Nur - Academia.edu (original) (raw)

Papers by N. Nur

Long-term studies conducted on breeding populations on the Farallon Islands (1971 to 2007) and in... more Long-term studies conducted on breeding populations on the Farallon Islands (1971 to 2007) and in the Point Reyes National Seashore (1980 to 2007), provide the means to characterize breeding phenology of seabird and landbird species and determine how that has changed over multiple temporal scales (variation among years, among decades, shifts in ocean regimes, etc.). However, to interpret phenological patterns and shifts requires information on the demography and ecological context of these species. Here we describe studies on three seabird species (Common Murre Uria aalge, Cassin's Auklet Ptychoramphus aleuticus, Brandt's Cormorant, Phalacrocorax penicillatus) where we have tied changes in breeding phenology, within a year, and among years, to demographic consequences (reproductive success, proportion of the population that breeds, adult survival, etc.). In addition, for these species we have information on diet choice of parents feeding chicks and how that has varied with...

... 4 pages 73-92 School of Natural Resources and Environment THE UNIVERSITY OF MICHIGAN Science ... more ... 4 pages 73-92 School of Natural Resources and Environment THE UNIVERSITY OF MICHIGAN Science Marc Bekoff 76 Survey of State Criteria Used to Determine the Status of Plant Taxa KyleDayton 82 Marine Matters Xantus ... economics (rush for patents, finan-cial gains). ...

Animal Behaviour, 1984

Non-territorial Intruders in the Great Tit: Are they Making The Best of a Bad Lot? Studies of the... more Non-territorial Intruders in the Great Tit: Are they Making The Best of a Bad Lot? Studies of the great tit, Parus major, in Belgium and Holland (Dhondt & Schillemans 1983, and references therein) reveal that some breeding pairs do not defend territories, and instead attempt to breed in nestboxes located within the defended territories of other great tit pairs, henceforth termed 'non-territorial intruders' (:'real intruders' in Dhondt & Schillemans 1983) and 'teiTitorial birds', respectively. A third class, 'territorial intruders', breed in nestboxes within another pair's territory, but defend a nearby territory. Dhondt & Schillemans (1983) argue that, relative to territorial birds (TN) and territorial intruders (TI), non-territorial intruders (NTI) 'have a much lower fitness'. Specifically, they estimate that the fitness of NTI individuals is 0.30, while the mean for TN and TI groups is 1.04 (see their Table VIII). In this note, I question the reliability of the fitness estimate for NTI birds: I argue that Dhondt & Schillemans greatly underestimate NTI fitness. Furthermore, I point out that their estimate is not consistent with their own interpretation, that NTI birds 'make the best of a bad situation'. Were we to accept their estimate we should, instead, conclude that NTI are making the worst of a bad situation, by employing tactics both suicidal and ineffectual. To obtain fitness values, Dhondt & Schillemans sum 'juvenile recruitment per adult' and 'adult survival'. They do not justify the summation procedure (but see Stenseth 1983; Nur 1984 for discussion and application of this procedure to field studies). It is, however, Dhondt & Schillemans' estimates of offspring recruitment and adult survival that lead to um-eliable and biased estimates of fitness. Difficulties with Dhondt & Schillemans' estimate of offspring recruitment (i.e. 1980 offspring observed breeding in 1981) per adult are as follows. (1) They count all NTI adults, even those deserting the nest during egglaying and incubation (4 such pairs); in a fifth nest, all nestlings died, presumably a result of desertion as well. Two of these pairs re-nested (in the study area); the other pairs may have re-nested, successfully, outside the study area. (2) Also problematic is Dhondt & Schillemarts' 'correction' of the offspring recruitment rate. Because only 8.9 % of 1980 fledglings were observed breeding the next year, and since 15 % of the fledglings must be recruited into the population to keep it stable, then presumably 6.1% of the fledglings bred in 1981 but were not identified. The latter group either dispersed to other areas or were in the study area but not identified (in 1980, only 82% of breeding adults were identified). Dhondt & Schillemans assume that whether a surviving offspring belonged to the 8.9 % or the 6.1% group was independent of its parents' territorial status, and therefore they multiplied observed recruitment by 1.7 (15%/8.9%)for all. However, inspection of their Table VII reveals that observed recruitment rate for TN was 9.3 %, for TI was 8.2% and for NTI was 6.1%. Dhondt & Schillemans reject the hypothesis that fledgling survival depends on territorial status (in support, fledgling weight, a good

In particular, population viability analyses have been developed for the congener piping plover C... more In particular, population viability analyses have been developed for the congener piping plover Charadrius melodus (Great Plains population: Ryan et al. 1993; Atlantic coast population: Melvin and Gibbs 1996). General Features of the Population Viability Analysis Model The model is stochastic. Stochasticity is one of the defining features of Population Viability Analyses in general (Burgman et al. 1993). Two types of random variation are incorporated: unpredictable variation in the environment and "demographic stochasticity." Demographic stochasticity can be thought of as follows: even if all relevant features of the environment (including predators, competitors, abiotic factors, etc.) impinging on western snowy plovers are known, and even though, on average, survival or reproductive success can be related to these environmental features, there will still be an element of unpredictability regarding the precise number of young or adults that survive or the number of fledglings produced in any time period. However, for the SFB subpopulation, no window survey has been carried out since 1991. Uncertainty about population trends since 1991 compounds uncertainty about current abundance. We therefore considered there to be an upper bound of 310 individuals (219 individuals observed on the window survey in 1991 x 1.286 x 1.1, to account for modest population growth since 1991) and a lower bound of 219 individuals (population decline since 1991, equal in magnitude to the undercounting during the window survey). For modeling, we used the mean of those two estimates (= 264 individuals). D-5 Conceptual Framework of the Model The key demographic parameters in the model are: (1) adult survival, (2) juvenile survival, (3) reproductive success, and (4) dispersal. All individuals 1 year or older are considered to be adult, and assumed to breed (see below). The demographic parameters are linked in the population model in the following manner, ignoring dispersal among subpopulations (detailed later) and ignoring any stochastic effects. The model keeps track of the abundance of each age class (1-year-old, 2-year-old, etc., up to 20year-old individuals) in each subpopulation. This enumeration by the model is carried out at the onset of the breeding season; this is referred to as a pre-breeding census. In the model, the number of 2-year-olds in year t+1, symbolized N(2) t+1 is equal to the number of 1-year-olds in year t, symbolized N(1) t , times the annual survival rate of 1-year-olds, symbolized S 1. Note that S 1 is not constant, but varies stochastically from year to year, and differs among subpopulations. Similar calculations are performed for the number of 3-year-olds, i.e., N(3) t+1 = N(2) t *S 2 , 4-year-olds, etc. In the model, adult survival is assumed to be the same for all ages, i.e., S 1 = S 2 = ... = S 19 , but no adult lives beyond 20 years of age, which is considered maximum age for this species. The number of 1-year-olds in a given year is equal to the number of fledged chicks produced the year before times the probability that a fledged chick will survive to reach the age of 1 year. If the total number of adults the year before is written N(A) t = N(1) t + N(2) t + ... + N(20) t , then the number of 1-year-olds in year t+1, symbolized N(1) t+1 , is equal to the product N(A) t *F*S 0 , where F is the number of male fledglings produced per male adult in each year, and S 0 is the probability a fledgling survives to 1 year (12 months) of age. Since the sex ratio of fledglings is unknown, we assume a 1:1 ratio. Any non-breeding among adults would act to reduce F; however, all adults are assumed to breed (see below). In the model, F and S 0 also vary among subpopulations and vary randomly among years, with a specified mean and standard deviation. Parameter Estimates Adult survival-The best estimates for adult survival came from capture/recapture analyses of Monterey Bay color-banded plovers, a major study population (henceforth Monterey Bay) situated within the MB subpopulation. Additional data for analyses came from color-banded study populations on Oregon beaches (Oregon) and San Diego beaches (San Diego). Note that we distinguish between study areas (Monterey Bay, Oregon and San Diego) and their respective, more inclusive subpopulations (MB, OR, SD). Analyses of survival were carried out using the program SURGE (Lebreton et al. 1992, Cooch et al. 1996) and for Monterey Bay were based on 777 adults D-6 (361 males, 416 females) followed over 14 years. Sample sizes for Oregon were 108 males and 70 females, followed over 8 years, and for San Diego 91 males and 137 females, followed over 4 years. Since male survival significantly exceeded female survival at Monterey Bay and only males were modeled, we present only estimates for male adults, for the Monterey Bay, Oregon and San Diego study populations. We fit a two-age class model for male adult survival, in which the first age class covers the first year after first capture, and the second age class covers all subsequent years. Estimates of survival for the first age class can be biased due to behavioral responses to trapping and banding, lower sitefidelity among some first-time captures, and other methodological difficulties. These biases do not apply to survival after the first year of banding (Pradel et al. 1997). For this reason, several studies have used only survival estimates from the second age class (e.g., Gaston 1992, Johnston et al. 1997); we adopted the same practice. Additional Assumptions Density Dependence-Not much is known about this, for any bird species. Following input from Western Snowy Plover Recovery Team members, we assume a limit on availability of beach habitat, i.e., that there is a region-specific limit on adequate nesting sites. Based on information provided by the recovery team, we estimate the limit, or ceiling, of breeding western snowy plovers to be:

… , and restoration. …, 2003

border remnant riparian habitats), 2) revegetating land with native trees, shrubs and understory,... more border remnant riparian habitats), 2) revegetating land with native trees, shrubs and understory, and 3) restoring natural river processes. The goals and strategies of the Project are consistent with those described in the Sacramento River Conservation Area Handbook (CA Resources Agency 2000). To maximize the success of the Project we are developing a multifaceted science program (Figure 1). The purpose of the program is to provide scientific understanding of ecosystem dynamics so that conservation actions can be critically evaluated and new restoration strategies can be developed. In this paper we provide an overview of some of the important projects that are currently underway and present

EXECUTIVE SUMMARY The vulnerability of species at risk from climate change is recognized as an im... more EXECUTIVE SUMMARY The vulnerability of species at risk from climate change is recognized as an important issue in California as well as globally. Assessing vulnerability requires information on the long-term viability of populations and understanding the ...

Levees: No levees. Channelization: One large channel with a few lateral ones. Very few small chan... more Levees: No levees. Channelization: One large channel with a few lateral ones. Very few small channels. Vegetation: Again dominated by Pickleweed, but with patches of Tule throughout and on the marsh fringes. Site Name: Pt. Edith. Bay: Suisun. County: Contra Costa Location: On south side of Suisun Bay. Crossing the Interstate 780 bridge to south after Benicia, turn on first exit and head east on Waterfront Road. Obtain permission to bird watch at the entrance kiosk at the site of the Port of Chicago. Park at the small parking lot created for Pt. Edith. The marsh we censused was to the east of the main north-south levee. Marsh History: The marsh was affected by the Shell Oil spill of 1988. Abundance oil residue remains today. Logistics: All points were accessed from the main levee, with one point on an old levee. Most all points were within 200 m of main levee. Levees: Many perpendicular levees come off main levee. Channelization: Some large channels exist, but much channelization occurs adjacent to levees. Vegetation: Tule vegetation and common cattail vegetation dominates. Patches of Pickleweed and Saltgrass are common as well.

ABSTRACT The large uncertainty associated with estimating the effects of sea-level rise and clima... more ABSTRACT The large uncertainty associated with estimating the effects of sea-level rise and climate change on tidal marsh ecosystems exacerbates the difficulty in planning for their effective conservation. To address this uncertainty, we modeled the distribution and abundance of tidal marsh bird species in the San Francisco Estuary for the period 2010 to 2110 in relation to projected changes in sea-level rise, salinity, and sediment availability using four future scenarios with assumptions of low or high suspended sediment concentrations and low or high rates of sea-level rise (0.52 or 1.65 m/100 yr). We used the projections of bird populations the modeled uncertainty to develop spatially explicit priorities for conservation and restoration using Zonation conservation planning software. In our models, marsh bird population generally declined from current levels due to the conversion of high and mid-marsh habitat to low-marsh and mudflats and changes in spring and summer salinity. High sea-level rise scenarios had the biggest impact on bird populations, although the effects were muted under high sediment availability scenarios. There was considerable variation in bird population projections among the four future scenarios we tested and the uncertainty tended to increase from 2030 to 2110. Because so little tidal marsh habitat currently remains in the San Francisco Estuary, the spatial prioritization found that all areas currently open to tidal influence were high priorities for conservation. We repeated this prioritization exercise with all barriers to tidal flow (e.g. levees) removed and identified important locations in which restoration by breaching levees would most efficiently provide long-term benefit to tidal marsh bird populations. The projected species distributions and changes in tidal marsh elevations are available in the form of interactive maps and downloadable GIS layers at: www.prbo.org/sfbayslr. This website can help managers plan effective conservation and restoration strategies to foster adaptation to the effects of future climate change.

Endangered Species Research, 2014

Understanding habitat preferences for endangered species is a high priority for management strate... more Understanding habitat preferences for endangered species is a high priority for management strategies to ensure minimum conflict between human uses and wildlife conservation. The purpose of this study was to identify oceanographic variables that predict occurrences of humpback whales Megaptera novaeangliae within the Cordell Bank and Gulf of the Farallones National Marine Sanctuaries, California, USA, to assess potential conflict with vessel traffic. We used data collected by Applied California Current Ecosystem Studies (ACCESS) conducted from 2004 to 2011. Using zero-inflated negative binomial regression, we developed predictive models and identified locations highly used by whales to characterize humpback whale habitat. We analyzed whale encounter rates at 3-km bin intervals in relation to bathymetric, surface and midwater hydrographic predictor variables and temporal variables characterizing oceanographic conditions. Our models included variables that accounted for detectability of whales. Two models were compared and contrasted: (1) a surface-only model, using only surface oceanographic variables, and (2) a surface + mid-water model, using both surface and mid-water variables. The surface + mid-water model performed significantly better than the surface-only model, which underestimated the amount of suitable whale habitat in the northern half of our study area. We compared resulting predicted habitat areas with previous and current San Francisco Bay Area shipping lane poly gonal footprints to investigate whether newly accepted changes in routes reduced areal overlap with humpback whale habitat. Although our analyses show that the area occupied by shipping traffic has decreased in areas of high predicted humpback whale habitat use, changes in vessel lane footprints do not account for several important aspects of ship-strike risk, including vessel frequency, speed, size and density patterns within the shipping lanes and variability between lanes.

Ecology, 1991

... 1983, Nur 1984, Coulson and Thomas 1985, Reid 1988, Boe-kelheide and Ainley 1989, Wooller et ... more ... 1983, Nur 1984, Coulson and Thomas 1985, Reid 1988, Boe-kelheide and Ainley 1989, Wooller et al. 1990, Syde-man et al. 1991; but see Pugesek 1981, 1983, 1984, Clutton-Brock 1984). ... 1991, but see Harvey et al. 1988, Clutton-Brock et al. 1989, Wooller et al. 1990). ...

Many migration monitoring stations cannot operate on every day of the migration period. In this p... more Many migration monitoring stations cannot operate on every day of the migration period. In this paper, we used migration count data from two stations (Point Reyes Bird Observatory fall migration and Long Point Bird Observatory spring migration) to examine the relationship between the proportion of count days (frequency of sampling) and the statistical power to detect long-term population trends. We found that power to detect trends at a single station declined at an accelerating rate as the frequency of sampling decreased. Stations that operate on one or two days per week are unlikely to detect changes in abundance for most species that would be well monitored at higher sampling frequencies. The effect of missing counts can be mitigated to some extent by the choice of sampling design (method of allocating count days over the migration period). We compared a number of candidate designs and found that systematic sampling was the most accurate, although stratifi ed random sampling may be preferred in situations where little is known about the pattern of migration. Designs that clump count days together, such as sampling only at weekends, should be avoided because adjacent count days tend to duplicate the same information.

Marine Ecology Progress Series, 2019

Wetlands, 2010

Tidal marsh monitoring and restoration can benefit from the union of fine-scale remote sensing pr... more Tidal marsh monitoring and restoration can benefit from the union of fine-scale remote sensing products and field-based survey data via spatial predictive models. As part of an interdisciplinary wetland monitoring project in San Francisco Bay, we developed a suite of 1-m pixel-level spatial metrics describing patterns in marsh vegetation and geomorphology for six sites across a large salinity gradient. These metrics, based on multi-spectral aerial imagery and derived vegetation maps, provided a basis for fine-scale spatial modeling of avian habitat potential. Using common yellowthroat (Geothlypis trichas), song sparrow (Melospiza melodia), and black rail (Later-allus jamaicensis) abundance data, we developed statistical models with relatively high explanatory power. In each case, models were improved by including vegetation-map variables, but variables directly extracted from aerial imagery were more reliable indicators of avian abundance. Although results varied by species, our models achieved reasonable within-site predictive success. When predicting to sites not used in the training set, however, validation results were inconsistent and often poor, suggesting that these models should be used with caution outside of the original study sites. As remotely sensed data become more readily available, our methods may be applied to a diverse range of sites, resulting in improved model generality and applicability.

PRBO Report to California …, 2009

PRBO Conservation Science conducted call-count surveys for California Clapper Rail (Rallus longir... more PRBO Conservation Science conducted call-count surveys for California Clapper Rail (Rallus longirostrus obsoletus) at 53 sites throughout the San Francisco Bay Estuary from 2005 through 2008. To maximize the spatial coverage of sites, surveys were ...

Quaternary International, 2013

Marine Ecology Progress Series, 2001

One of the longest continuing data sets involving a marine organism in the Antarctic is that of a... more One of the longest continuing data sets involving a marine organism in the Antarctic is that of annual estimates of breeding population size of Adélie penguins Pygoscelis adeliae at colonies on Ross Island, Ross Sea, 1959 to 1997. The sizes of these colonies have displayed significant interannual variability during the 29-yr period. We hypothesized that changes are related to natural environmental factors; and used path analysis to analyze annual variation in population growth in relation to physical environmental factors during that part of the record with comparable sea-ice satellite imagery from 1973 to 1997. The Ross Sea sector of the Southern Ocean lying north of Ross Island, from 150°E to 130°W, comprised our study area. Annual population growth measured during summer was explained best, and inversely, by the extent of sea-ice in the study area 5 winters earlier, and in some way related to the Southern Oscillation. Analysis of a subset of the sea-ice data from 1979 to 1997 indicated strong correlations to ice conditions in the eastern portion of the study area (174 to 130°W), and virtually no correlations to the western half (150°E to 175°W). This result supported other indirect evidence that the Ross Island penguins winter in the eastern Ross Sea/western Amundsen Sea. A demographic model indicated that variation in survival of juveniles and subadults might account for the observed population variation, and would also explain the 5-yr lag as 5 yr is the average age of recruitment to the summer breeding population. Extensive sea-ice during winter appears to reduce subadult survival, expressed subsequently when these cohorts reach maturation. We hypothesize that extensive (more northerly) sea-ice limits access of penguins to productive waters known to occur south of the southern boundary of the Antarctic Circumpolar Current, with starvation or increased predation disproportionately affecting less-experienced birds. The observed patterns of penguin population change, including those preceding the satellite era, imply that sea-ice extent has changed significantly over recent decades.

Marine Ecology Progress Series, 2010

Animals modulate breeding effort by balancing investment in self-maintenance against investment i... more Animals modulate breeding effort by balancing investment in self-maintenance against investment in their young, potentially impacting reproductive success when faced with difficult conditions. This life history trade-off model has been evaluated for flying birds, especially those that forage over large pelagic regions of relatively sparse prey availability. We evaluated its applicability to penguins which, lacking flight, depend on reliably available prey relatively close to colonies. We used transponders and an automated weighing system to monitor 40 to 75 breeding Adélie penguins Pygoscelis adeliae per season for 10 seasons, while environmental conditions varied dramatically, measuring foraging trip duration, parental mass change, and total food load delivered to chicks. Parents that lost the most mass during breeding provided more food to chicks while maintaining their own condition. In contrast, in years when adult mass was lower to begin with, parents recovered their own condition and delivered less food to chicks. Food loads were also related to environmental variables, with parents making longer trips and delivering less food when access to prey was more difficult, but delivering more food to 2-chick broods than to 1-chick broods. Penguins did not alternate between short (chick provisioning) and long (self-maintenance) trips, as has been observed in farranging seabirds. Nevertheless, our results indicate they regulated their condition depending on environmental and physiological factors, with impacts on the amount of food delivered to young and pre-fledging mass. Parental choice of multiple foraging habitats and depletion of prey in the nearest habitat due to intraspecific competition have important implications in explaining contrasting patterns observed among studies investigating the life history trade-off model in birds.

ICES Journal of Marine Science, 2008

Roth, J. E., Nur, N., Warzybok, P., and Sydeman, W. J. 2008. Annual prey consumption of a dominan... more Roth, J. E., Nur, N., Warzybok, P., and Sydeman, W. J. 2008. Annual prey consumption of a dominant seabird, the common murre, in the California Current system. – ICES Journal of Marine Science, 65: 1046–1056. Information compiled from the literature on population size, diet composition, field metabolic rate, prey energy densities, and assimilation efficiency is used to estimate annual prey consumption by common murres (Uria aalge), between Cape Blanco, OR, and Point Conception, CA, USA. The population consumed an estimated 172 313 t of prey based on population estimates and diet data from the mid- to the late 1980s, including 50 125 t consumed by breeding adults, 36 940 t by non-breeding birds during the breeding season, 85 098 t by all birds during the wintering period, and 150 t by dependent chicks before their leaving the breeding colonies. The population in the mid-2000s consumed 225 235 t of prey based on population estimates from 2004, including 65 516 t consumed by breeding a...