We examined the response of apparent adult survivorship to light and noise. Staff and volunteers of the Neighborhood Nestwatch Program (NN), a citizen science project run by the Smithsonian Migratory Bird Center, provided avian count data from 2000 to 2020. With sampling predominately located at the homes of project participants, NN sampling sites were within a 100-km spatial scale encompassing a rural-to-urban land-use gradient in the greater Washington, D.C., USA, metropolitan region. Project participant sites were chosen based on their position along the rural-to-urban gradient as assessed by the proportion of impervious surface; sites were defined as a 100-m radius area surrounding each sampling location (described below). NN sites (n = 242) included private residences, community centers, and schools, as well as sites within forested and agricultural land cover. By incorporating privately owned land within the study design, we captured portions of the urban and suburban matrix not normally monitored in avian survivorship studies. NN sites were representative of the urban-rural gradient within the study area, as documented by Evans et al. (2015).
NN technicians visited sites once annually during the avian breeding season (May-August). To mitigate between-site differences, visit dates were scheduled such that sites visited early in the breeding season in a given year were visited late on the following year. NN technicians captured adult birds with mist netting with a combination of territorial intrusion playback and mobbing call playback. Individuals of seven focal species were marked with a unique U.S. Fish and Wildlife Service aluminum band and a unique combination of colored plastic bands. During each banding visit, technicians spent one hour attempting to re-sight previously captured individuals within a 200-m radius of the banding station using the playback techniques as described above. Project participants searched for color-banded birds throughout the year and reported observations to NN. Participant resights accounted for the majority of re-encounters (55%, n = 2,263).
For each of the 242 NN sites, we extracted corresponding data from the georeferenced maps of light pollution, noise pollution, and impervious surface (Fig. 1). Using Pearson Correlation Coefficients, we determined that light, noise, and impervious surface were correlated (Table 1).
Table 1
Correlation among impervious surface, light pollution, and noise pollution for 242 sample sites in the Neighborhood Nestwatch program, Washington DC (2000–2020).
| IMP | noise | light |
IMP | 1.0000000 | 0.7922362 | 0.8219412 |
noise | 0.7922362 | 1.0000000 | 0.8480927 |
light | 0.8219412 | 0.8480927 | 1.0000000 |
Following Sensaki et al. (2020), we used data from the second world atlas of artificial night sky brightness converted to 270-m resolution (Falchi et al. 2016). Estimates of light pollution were the zenith anthropic sky brightness as a ratio to the natural background sky brightness. Light pollution estimates provided a single, average value across an entire pixel and all light data was considered equally. For example, an area with many houses or only one airport could emit similar levels of light.
We used anthropogenic noise data from a georeferenced map of expected sound pressure levels (Mennitt et al. 2016). These data model natural sound levels from biotic and physiographic sources and compute anthropogenic noise exceedance levels. Following Senzaki et al. (2020), we used anthropogenic daytime A-weighted L50 sound pressure levels as the estimate of anthropogenic noise.
We examined the influence of light and noise on the annual survival of seven species of birds most common across the development gradient within the study region: American Robin, Carolina Chickadee (Poecile carolinensis), Carolina Wren, Gray Catbird, House Wren, Northern Cardinal, and Song Sparrow. We investigated the effects of light and noise on apparent survivorship (Φ) and detection probability by fitting Cormack-Jolly-Seber survivorship models to these data. Detection probability was assumed to be constant across sites and years. Time-varying estimates of detection and survival were not achievable due to within-year sample size constraints. We used program MARK (White and Burnham 1999) to build descriptive models and compare their fit to the data according to Akaike's Information Criterion (AIC; Akaike 1973) to estimate annual survival of the seven focal species at each site. We built models of adult survival that incorporated combinations of individual covariates (light, noise, and impervious surface) and ran species-specific models to determine the relative effect of our urbanization metrics on adult survival.
Because Evans et al. (2015) showed that avian adult survival in response to urbanization was often nonlinear, we included both linear (IMP) and quadratic (IMP2) impervious terms as model covariates (Table 2). Covariates used in model construction (see Table 2) were standardized as z-scores \(\left(\frac{x-\mu }{\sigma }\right)\). We used Akaike’s information criterion (AIC; Akaike 1973) to select the best models among a set of biologically plausible candidate models. We selected the model with the smallest ΔAICc as the best among all models being compared. Additionally, we used normalized AIC weights, the ratio of the likelihood of a given model relative to the sum of the likelihood across models, to evaluate the weight of evidence for a given model relative to the full set of candidate models. We used likelihood ratios (neg2lnl), the comparison of nested models, to evaluate the number of parameters (npar) of each model. When choosing the best model, we considered support based on ΔAICc, AIC weights, and neg2lnl (Johnson et al. 2004).
Table 2
Variables used in the development of a priori light pollution and noise pollution models for apparent survivorship (Φ).
Model Set | Variable | Variable description |
a priori | Sex | binary sex (male, female) |
Urbanization | IMP | Impervious surface cover (%) |
Urbanization | IMP2 | Impervious surface, quadratic form |
Light Pollution | light | Anthropogenic light pollution along an urbanization gradient |
Noise Pollution | noise | Anthropogenic noise pollution along an urbanization gradient |
To account for variation or potential bias in the estimates of detectability and survivorship when analyzing the effect of light pollution and noise pollution on apparent survival, we constructed an a priori model for each species that included sex. Territorial males may be more likely to be encountered than females due to behavioral differences (Amrhein et al. 2012); therefore, sex was included as a binary dummy covariate for estimating detectability. We then ranked the a priori model (sex) for each species based on AIC weights with combinations of models that included impervious surface and noise and light levels.
Because model selection and subsequent parameter estimates can become unstable (high variance) by over-fitting models (~ 10 parameters), especially when there is an insufficient sample size for an individual group variable (Breiman 1996, Burnham and Anderson 2002), we constrained our model set to those in which the parameter estimates were identifiable (Table 3). Here we are referring to extrinsic identifiability, where parameter estimates are at or near their boundary (0 or 1) or are otherwise unidentifiable because of insufficient sample size. Ultimately, we excluded these ‘‘over-parameterized’’ models that contained more parameters than could be accommodated by the data. Therefore, not all covariates could be included in a priori models for each species. We chose to present the model betas from the lowest ΔAICc of each a priori model for each species.
Table 3
Summary statistics for the candidate models examining the impact of anthropogenic light and anthropogenic noise on avian survival within the greater Washington, D.C., area; models were ranked by AICc and log likelihood vales are given.
Species Code | Model φ | k | AICc | ΔAICc | w | -2LogLik |
AMRO | light | 4 | 724.30 | 0.00 | 0.16 | 716.30 |
| IMP + IMP2 + light | 6 | 724.72 | 0.42 | 0.13 | 712.72 |
| IMP + IMP2 | 5 | 725.32 | 1.02 | 0.10 | 715.32 |
| IMP + IMP2 + light + noise | 7 | 725.40 | 1.11 | 0.09 | 711.40 |
| IMP + light | 5 | 726.24 | 1.94 | 0.06 | 716.24 |
CACH | IMP + IMP2 | 5 | 1280.40 | 0.00 | 0.14 | 1270.41 |
| IMP | 4 | 1280.94 | 0.53 | 0.11 | 1272.94 |
| sex + IMP + IMP2 | 6 | 1281.86 | 1.45 | 0.07 | 1269.86 |
| Intercept | 3 | 1281.87 | 1.46 | 0.06 | 1275.87 |
| IMP + IMP2 + light | 6 | 1281.92 | 1.51 | 0.07 | 1269.92 |
CARW | sex + IMP + IMP2 | 6 | 1263.94 | 0.00 | 0.13 | 1251.94 |
| sex | 4 | 1264.00 | 0.05 | 0.13 | 1256 |
| sex + IMP | 5 | 1264.39 | 0.45 | 0.11 | 1254.39 |
| sex + noise | 5 | 1264.87 | 0.93 | 0.08 | 1254.87 |
| sex + IMP + IMP2 + light | 7 | 1265.37 | 1.42 | 0.06 | 1251.37 |
GRCA | sex + IMP + IMP2 + + light | 7 | 2529.95 | 0.00 | 3.29 | 2515.95 |
| sex + IMP + IMP2 + light + noise | 8 | 2529.95 | 0.00 | 2.81 | 2515.95 |
| sex + IMP + IMP2 | 6 | 2530.77 | 0.82 | 2.17 | 2518.77 |
| sex + IMP + IMP2 + noise | 7 | 2532.74 | 2.79 | 8.80 | 2518.74 |
| IMP + IMP2 + light | 6 | 2534.53 | 4.59 | 3.3 | 2522.53 |
HOWR | IMP + IMP2 + light | 6 | 907.06 | 0.00 | 0.37 | 895.06 |
| sex + IMP + IMP2 + light | 7 | 907.72 | 0.65 | 0.27 | 893.72 |
| IMP + IMP2 + light + noise | 7 | 909.05 | 2.0 | 0.14 | 895.05 |
| sex + IMP + IMP2 + light + noise | 8 | 909.71 | 2.65 | 0.10 | 893.71 |
| IMP + light | 5 | 912.06 | 5.00 | 0.03 | 902.06 |
NOCA | sex + IMP | 5 | 3855.79 | 0.00 | 0.17 | 3845.79 |
| sex + IMP + light | 6 | 3856.24 | 0.45 | 0.14 | 3844.24 |
| sex | 4 | 3856.74 | 0.95 | 0.11 | 3848.74 |
| sex + IMP + light | 6 | 3857.47 | 1.69 | 0.07 | 3845.47 |
| Sex + IMP + IMP2 | 6 | 3857.59 | 1.81 | 0.07 | 3845.59 |
SOSP | IMP + IMP2 | 5 | 2034.34 | 0.00 | 0.18 | 2024.34 |
| IMP + IMP2 + light + noise | 7 | 2034.58 | 0.24 | 0.16 | 2020.58 |
| sex + IMP + IMP2 | 6 | 2035.39 | 1.06 | 0.10 | 223.39 |
| sex + IMP2 + noise | 6 | 2035.65 | 1.32 | 0.09 | 2023.65 |
| IMP + IMP2 + light | 6 | 2035.74 | 1.41 | 0.09 | 2023.74 |