Receive strange symbols in XBee network

Using Arduino Programming Questions
#1

I’m running sensor network with base station (which consists of XBee Explorer and XBee Series 2) and two sensor nodes (each one consists of Arduino Mega, Wireless Proto Shield, XBee Series 2 and temperature sensor TMP102). I’m using this code for each node:

#include <Wire.h>
int tmp102Address = 0x48;

void setup(){
  Serial.begin(9600);
  Wire.begin();
}

void loop(){

  float celsius = getTemperature();
  Serial.print("NODE 1");
  Serial.print("\n");
  Serial.print("Celsius: ");
  Serial.println(celsius);

  delay(7000); 
}

float getTemperature(){
  Wire.requestFrom(tmp102Address,2); 

  byte MSB = Wire.read();
  byte LSB = Wire.read();

    int TemperatureSum = ((MSB << 8) | LSB) >> 4; 

  float celsius = TemperatureSum*0.0625;
  return celsius;
}

The serial monitor displays correctly the data from each node when I chose the appropriate serial port. But when I’m using serial monitor for the base station port there are strange received symbols between sensors’ data:

I appreciate any help!

#2